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23 .\" Arch: generic
24 .\" Software: JDK 8
25 .\" Date: 03 March 2015
26 .\" SectDesc: Basic Tools
27 .\" Title: javac.1
28 .\"
29 .if n .pl 99999
30 .TH javac 1 "03 March 2015" "JDK 8" "Basic Tools"
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35 .\" http://bugs.debian.org/507673
36 .\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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46 .ad l
47 .\" -----------------------------------------------------------------
48 .\" * MAIN CONTENT STARTS HERE *
49 .\" -----------------------------------------------------------------
50
51 .SH NAME
52 javac \- Reads Java class and interface definitions and compiles them into bytecode and class files\&.
53 .SH SYNOPSIS
54 .sp
55 .nf
56
57 \fBjavac\fR [ \fIoptions\fR ] [ \fIsourcefiles\fR ] [ \fIclasses\fR] [ \fI@argfiles\fR ]
58 .fi
59 .sp
60 Arguments can be in any order:
61 .TP
62 \fIoptions\fR
63 Command-line options\&. See Options\&.
64 .TP
65 \fIsourcefiles\fR
66 One or more source files to be compiled (such as \f3MyClass\&.java\fR)\&.
67 .TP
68 \fIclasses\fR
69 One or more classes to be processed for annotations (such as \f3MyPackage\&.MyClass\fR)\&.
70 .TP
71 \fI@argfiles\fR
72 One or more files that list options and source files\&. The \f3-J\fR options are not allowed in these files\&. See Command-Line Argument Files\&.
73 .SH DESCRIPTION
74 The \f3javac\fR command reads class and interface definitions, written in the Java programming language, and compiles them into bytecode class files\&. The \f3javac\fR command can also process annotations in Java source files and classes\&.
75 .PP
76 There are two ways to pass source code file names to \f3javac\fR\&.
77 .TP 0.2i
78 \(bu
79 For a small number of source files, list the file names on the command line\&.
80 .TP 0.2i
81 \(bu
82 For a large number of source files, list the file names in a file that is separated by blanks or line breaks\&. Use the list file name preceded by an at sign (@) with the \f3javac\fR command\&.
83 .PP
84 Source code file names must have \&.java suffixes, class file names must have \&.class suffixes, and both source and class files must have root names that identify the class\&. For example, a class called \f3MyClass\fR would be written in a source file called \f3MyClass\&.java\fR and compiled into a bytecode class file called \f3MyClass\&.class\fR\&.
85 .PP
86 Inner class definitions produce additional class files\&. These class files have names that combine the inner and outer class names, such as \f3MyClass$MyInnerClass\&.class\fR\&.
87 .PP
88 Arrange source files in a directory tree that reflects their package tree\&. For example, if all of your source files are in \f3/workspace\fR, then put the source code for \f3com\&.mysoft\&.mypack\&.MyClass\fR in \f3/workspace/com/mysoft/mypack/MyClass\&.java\fR\&.
89 .PP
90 By default, the compiler puts each class file in the same directory as its source file\&. You can specify a separate destination directory with the \f3-d\fR option\&.
91 .SH OPTIONS
92 The compiler has a set of standard options that are supported on the current development environment\&. An additional set of nonstandard options are specific to the current virtual machine and compiler implementations and are subject to change in the future\&. Nonstandard options begin with the \f3-X\fR option\&.
93 .TP 0.2i
94 \(bu
95 See also Cross-Compilation Options
96 .TP 0.2i
97 \(bu
98 See also Nonstandard Options
99 .SS STANDARD\ OPTIONS
100 .TP
101 -A\fIkey\fR[\fI=value\fR]
102 .br
103 Specifies options to pass to annotation processors\&. These options are not interpreted by \f3javac\fR directly, but are made available for use by individual processors\&. The \f3key\fR value should be one or more identifiers separated by a dot (\&.)\&.
104 .TP
105 -cp \fIpath\fR or -classpath \fIpath\fR
106 .br
107 Specifies where to find user class files, and (optionally) annotation processors and source files\&. This class path overrides the user class path in the \f3CLASSPATH\fR environment variable\&. If neither \f3CLASSPATH\fR, \f3-cp\fR nor \f3-classpath\fR is specified, then the user \fIclass path\fR is the current directory\&. See Setting the Class Path\&.
108
109 If the \f3-sourcepath\fR option is not specified, then the user class path is also searched for source files\&.
110
111 If the \f3-processorpath\fR option is not specified, then the class path is also searched for annotation processors\&.
112 .TP
113 -Djava\&.ext\&.dirs=\fIdirectories\fR
114 .br
115 Overrides the location of installed extensions\&.
116 .TP
117 -Djava\&.endorsed\&.dirs=\fIdirectories\fR
118 .br
119 Overrides the location of the endorsed standards path\&.
120 .TP
121 -d \fIdirectory\fR
122 .br
123 Sets the destination directory for class files\&. The directory must already exist because \f3javac\fR does not create it\&. If a class is part of a package, then \f3javac\fR puts the class file in a subdirectory that reflects the package name and creates directories as needed\&.
124
125 If you specify \f3-d\fR\f3/home/myclasses\fR and the class is called \f3com\&.mypackage\&.MyClass\fR, then the class file is \f3/home/myclasses/com/mypackage/MyClass\&.class\fR\&.
126
127 If the \fI-d\fR option is not specified, then \f3javac\fR puts each class file in the same directory as the source file from which it was generated\&.
128
129 \fINote:\fR The directory specified by the \fI-d\fR option is not automatically added to your user class path\&.
130 .TP
131 -deprecation
132 .br
133 Shows a description of each use or override of a deprecated member or class\&. Without the \f3-deprecation\fR option, \f3javac\fR shows a summary of the source files that use or override deprecated members or classes\&. The \f3-deprecation\fR option is shorthand for \f3-Xlint:deprecation\fR\&.
134 .TP
135 -encoding \fIencoding\fR
136 .br
137 Sets the source file encoding name, such as EUC-JP and UTF-8\&. If the \f3-encoding\fR option is not specified, then the platform default converter is used\&.
138 .TP
139 -endorseddirs \fIdirectories\fR
140 .br
141 Overrides the location of the endorsed standards path\&.
142 .TP
143 -extdirs \fIdirectories\fR
144 .br
145 Overrides the location of the \f3ext\fR directory\&. The directories variable is a colon-separated list of directories\&. Each JAR file in the specified directories is searched for class files\&. All JAR files found become part of the class path\&.
146
147 If you are cross-compiling (compiling classes against bootstrap and extension classes of a different Java platform implementation), then this option specifies the directories that contain the extension classes\&. See Cross-Compilation Options for more information\&.
148 .TP
149 -g
150 .br
151 Generates all debugging information, including local variables\&. By default, only line number and source file information is generated\&.
152 .TP
153 -g:none
154 .br
155 Does not generate any debugging information\&.
156 .TP
157 -g:[\fIkeyword list\fR]
158 .br
159 Generates only some kinds of debugging information, specified by a comma separated list of keywords\&. Valid keywords are:
160 .RS
161 .TP
162 source
163 Source file debugging information\&.
164 .TP
165 lines
166 Line number debugging information\&.
167 .TP
168 vars
169 Local variable debugging information\&.
170 .RE
171
172 .TP
173 -help
174 .br
175 Prints a synopsis of standard options\&.
176 .TP
177 -implicit:[\fIclass, none\fR]
178 .br
179 Controls the generation of class files for implicitly loaded source files\&. To automatically generate class files, use \f3-implicit:class\fR\&. To suppress class file generation, use \f3-implicit:none\fR\&. If this option is not specified, then the default is to automatically generate class files\&. In this case, the compiler issues a warning if any such class files are generated when also doing annotation processing\&. The warning is not issued when the \f3-implicit\fR option is set explicitly\&. See Searching for Types\&.
180 .TP
181 -J\fIoption\fR
182 .br
183 Passes \f3option\fR to the Java Virtual Machine (JVM), where option is one of the options described on the reference page for the Java launcher\&. For example, \f3-J-Xms48m\fR sets the startup memory to 48 MB\&. See java(1)\&.
184
185 \fINote:\fR The \fICLASSPATH\fR, \f3-classpath\fR, \f3-bootclasspath\fR, and \f3-extdirs\fR options do not specify the classes used to run \f3javac\fR\&. Trying to customize the compiler implementation with these options and variables is risky and often does not accomplish what you want\&. If you must customize the complier implementation, then use the \f3-J\fR option to pass options through to the underlying \f3\fRJava launcher\&.
186 .TP
187 -nowarn
188 .br
189 Disables warning messages\&. This option operates the same as the \f3-Xlint:none\fR option\&.
190 .TP
191 -parameters
192 .br
193 Stores formal parameter names of constructors and methods in the generated class file so that the method \f3java\&.lang\&.reflect\&.Executable\&.getParameters\fR from the Reflection API can retrieve them\&.
194 .TP
195 -proc: [\fInone\fR, \fIonly\fR]
196 .br
197 Controls whether annotation processing and compilation are done\&. \f3-proc:none\fR means that compilation takes place without annotation processing\&. \f3-proc:only\fR means that only annotation processing is done, without any subsequent compilation\&.
198 .TP
199 -processor \fIclass1\fR [,\fIclass2\fR,\fIclass3\fR\&.\&.\&.]
200 .br
201 Names of the annotation processors to run\&. This bypasses the default discovery process\&.
202 .TP
203 -processorpath \fIpath\fR
204 .br
205 Specifies where to find annotation processors\&. If this option is not used, then the class path is searched for processors\&.
206 .TP
207 -s \fIdir\fR
208 .br
209 Specifies the directory where to place the generated source files\&. The directory must already exist because \f3javac\fR does not create it\&. If a class is part of a package, then the compiler puts the source file in a subdirectory that reflects the package name and creates directories as needed\&.
210
211 If you specify \f3-s /home/mysrc\fR and the class is called \f3com\&.mypackage\&.MyClass\fR, then the source file is put in \f3/home/mysrc/com/mypackage/MyClass\&.java\fR\&.
212 .TP
213 -source \fIrelease\fR
214 .br
215 Specifies the version of source code accepted\&. The following values for \f3release\fR are allowed:
216 .RS
217 .TP
218 1\&.3
219 The compiler does not support assertions, generics, or other language features introduced after Java SE 1\&.3\&.
220 .TP
221 1\&.4
222 The compiler accepts code containing assertions, which were introduced in Java SE 1\&.4\&.
223 .TP
224 1\&.5
225 The compiler accepts code containing generics and other language features introduced in Java SE 5\&.
226 .TP
227 5
228 Synonym for 1\&.5\&.
229 .TP
230 1\&.6
231 No language changes were introduced in Java SE 6\&. However, encoding errors in source files are now reported as errors instead of warnings as in earlier releases of Java Platform, Standard Edition\&.
232 .TP
233 6
234 Synonym for 1\&.6\&.
235 .TP
236 1\&.7
237 The compiler accepts code with features introduced in Java SE 7\&.
238 .TP
239 7
240 Synonym for 1\&.7\&.
241 .TP
242 1\&.8
243 This is the default value\&. The compiler accepts code with features introduced in Java SE 8\&.
244 .TP
245 8
246 Synonym for 1\&.8\&.
247 .RE
248
249 .TP
250 -sourcepath \fIsourcepath\fR
251 .br
252 Specifies the source code path to search for class or interface definitions\&. As with the user class path, source path entries are separated by colons (:) on Oracle Solaris and semicolons on Windows and can be directories, JAR archives, or ZIP archives\&. If packages are used, then the local path name within the directory or archive must reflect the package name\&.
253
254 \fINote:\fR Classes found through the class path might be recompiled when their source files are also found\&. See Searching for Types\&.
255 .TP
256 -verbose
257 .br
258 Uses verbose output, which includes information about each class loaded and each source file compiled\&.
259 .TP
260 -version
261 .br
262 Prints release information\&.
263 .TP
264 -werror
265 .br
266 Terminates compilation when warnings occur\&.
267 .TP
268 -X
269 .br
270 Displays information about nonstandard options and exits\&.
271 .SS CROSS-COMPILATION\ OPTIONS
272 By default, classes are compiled against the bootstrap and extension classes of the platform that \f3javac\fR shipped with\&. But \f3javac\fR also supports cross-compiling, where classes are compiled against a bootstrap and extension classes of a different Java platform implementation\&. It is important to use the \f3-bootclasspath\fR and \f3-extdirs\fR options when cross-compiling\&.
273 .TP
274 -target \fIversion\fR
275 .br
276 Generates class files that target a specified release of the virtual machine\&. Class files will run on the specified target and on later releases, but not on earlier releases of the JVM\&. Valid targets are 1\&.1, 1\&.2, 1\&.3, 1\&.4, 1\&.5 (also 5), 1\&.6 (also 6), 1\&.7 (also 7), and 1\&.8 (also 8)\&.
277
278 The default for the \f3-target\fR option depends on the value of the \f3-source\fR option:
279 .RS
280 .TP 0.2i
281 \(bu
282 If the \f3-source\fR option is not specified, then the value of the \f3-target\fR option is 1\&.8
283 .TP 0.2i
284 \(bu
285 If the \f3-source\fR option is 1\&.2, then the value of the \f3-target\fR option is 1\&.4
286 .TP 0.2i
287 \(bu
288 If the \f3-source\fR option is 1\&.3, then the value of the \f3-target\fR option is 1\&.4
289 .TP 0.2i
290 \(bu
291 If the \f3-source\fR option is 1\&.5, then the value of the \f3-target\fR option is 1\&.8
292 .TP 0.2i
293 \(bu
294 If the \f3-source\fR option is 1\&.6, then the value of the \f3-target\fR is option 1\&.8
295 .TP 0.2i
296 \(bu
297 If the \f3-source\fR option is 1\&.7, then the value of the \f3-target\fR is option 1\&.8
298 .TP 0.2i
299 \(bu
300 For all other values of the \f3-source\fR option, the value of the \f3-target\fR option is the value of the \f3-source\fR option\&.
301 .RE
302
303 .TP
304 -bootclasspath \fIbootclasspath\fR
305 .br
306 Cross-compiles against the specified set of boot classes\&. As with the user class path, boot class path entries are separated by colons (:) and can be directories, JAR archives, or ZIP archives\&.
307 .SS COMPACT\ PROFILE\ OPTION
308 Beginning with JDK 8, the \f3javac\fR compiler supports compact profiles\&. With compact profiles, applications that do not require the entire Java platform can be deployed and run with a smaller footprint\&. The compact profiles feature could be used to shorten the download time for applications from app stores\&. This feature makes for more compact deployment of Java applications that bundle the JRE\&. This feature is also useful in small devices\&.
309 .PP
310 The supported profile values are \f3compact1\fR, \f3compact2\fR, and \f3compact3\fR\&. These are additive layers\&. Each higher-numbered compact profile contains all of the APIs in profiles with smaller number names\&.
311 .TP
312 -profile
313 .br
314 When using compact profiles, this option specifies the profile name when compiling\&. For example:
315 .sp
316 .nf
317 \f3javac \-profile compact1 Hello\&.java\fP
318 .fi
319 .nf
320 \f3\fP
321 .fi
322 .sp
323
324
325 javac does not compile source code that uses any Java SE APIs that is not in the specified profile\&. Here is an example of the error message that results from attempting to compile such source code:
326 .sp
327 .nf
328 \f3cd jdk1\&.8\&.0/bin\fP
329 .fi
330 .nf
331 \f3\&./javac \-profile compact1 Paint\&.java\fP
332 .fi
333 .nf
334 \f3Paint\&.java:5: error: Applet is not available in profile \&'compact1\&'\fP
335 .fi
336 .nf
337 \f3import java\&.applet\&.Applet;\fP
338 .fi
339 .nf
340 \f3\fP
341 .fi
342 .sp
343
344
345 In this example, you can correct the error by modifying the source to not use the \f3Applet\fR class\&. You could also correct the error by compiling without the -profile option\&. Then the compilation would be run against the full set of Java SE APIs\&. (None of the compact profiles include the \f3Applet\fR class\&.)
346
347 An alternative way to compile with compact profiles is to use the \f3-bootclasspath\fR option to specify a path to an \f3rt\&.jar\fR file that specifies a profile\&'s image\&. Using the \f3-profile\fR option instead does not require a profile image to be present on the system at compile time\&. This is useful when cross-compiling\&.
348 .SS NONSTANDARD\ OPTIONS
349 .TP
350 -Xbootclasspath/p:\fIpath\fR
351 .br
352 Adds a suffix to the bootstrap class path\&.
353 .TP
354 -Xbootclasspath/a:\fIpath\fR
355 .br
356 Adds a prefix to the bootstrap class path\&.
357 .TP
358 -Xbootclasspath/:\fIpath\fR
359 .br
360 Overrides the location of the bootstrap class files\&.
361 .TP
362 -Xdoclint:[-]\fIgroup\fR [\fI/access\fR]
363 .br
364 Enables or disables specific groups of checks, where \fIgroup\fR is one of the following values: \f3accessibility\fR, \f3syntax\fR, \f3reference\fR, \f3html\fR or \f3missing\fR\&. For more information about these groups of checks see the \f3-Xdoclint\fR option of the \f3javadoc\fR command\&. The \f3-Xdoclint\fR option is disabled by default in the \f3javac\fR command\&.
365
366 The variable \fIaccess\fR specifies the minimum visibility level of classes and members that the \f3-Xdoclint\fR option checks\&. It can have one of the following values (in order of most to least visible) : \f3public\fR, \f3protected\fR, \f3package\fR and \f3private\fR\&. For example, the following option checks classes and members (with all groups of checks) that have the access level protected and higher (which includes protected, package and public):
367 .sp
368 .nf
369 \f3\-Xdoclint:all/protected\fP
370 .fi
371 .nf
372 \f3\fP
373 .fi
374 .sp
375
376
377 The following option enables all groups of checks for all access levels, except it will not check for HTML errors for classes and members that have access level package and higher (which includes package and public):
378 .sp
379 .nf
380 \f3\-Xdoclint:all,\-html/package\fP
381 .fi
382 .nf
383 \f3\fP
384 .fi
385 .sp
386
387 .TP
388 -Xdoclint:none
389 .br
390 Disables all groups of checks\&.
391 .TP
392 -Xdoclint:all[\fI/access\fR]
393 .br
394 Enables all groups of checks\&.
395 .TP
396 -Xlint
397 .br
398 \fI\fREnables all recommended warnings\&. In this release, enabling all available warnings is recommended\&.
399 .TP
400 -Xlint:all
401 .br
402 \fI\fREnables all recommended warnings\&. In this release, enabling all available warnings is recommended\&.
403 .TP
404 -Xlint:none
405 .br
406 Disables all warnings\&.
407 .TP
408 -Xlint:\fIname\fR
409 .br
410 Disables warning name\&. See Enable or Disable Warnings with the -Xlint Option for a list of warnings you can disable with this option\&.
411 .TP
412 -Xlint:\fI-name\fR
413 .br
414 Disables warning name\&. See Enable or Disable Warnings with the -Xlint Option with the \f3-Xlint\fR option to get a list of warnings that you can disable with this option\&.
415 .TP
416 -Xmaxerrs \fInumber\fR
417 .br
418 Sets the maximum number of errors to print\&.
419 .TP
420 -Xmaxwarns \fInumber\fR
421 .br
422 Sets the maximum number of warnings to print\&.
423 .TP
424 -Xstdout \fIfilename\fR
425 .br
426 Sends compiler messages to the named file\&. By default, compiler messages go to \f3System\&.err\fR\&.
427 .TP
428 -Xprefer:[\fInewer,source\fR]
429 .br
430 Specifies which file to read when both a source file and class file are found for a type\&. (See Searching for Types)\&. If the \f3-Xprefer:newer\fR option is used, then it reads the newer of the source or class file for a type (default)\&. If the \f3-Xprefer:source\fR option is used, then it reads the source file\&. Use -\f3Xprefer:source\fR when you want to be sure that any annotation processors can access annotations declared with a retention policy of \f3SOURCE\fR\&.
431 .TP
432 -Xpkginfo:[\fIalways\fR,\fIlegacy\fR,\fInonempty\fR]
433 .br
434 Control whether javac generates \f3package-info\&.class\fR files from package-info\&.java files\&. Possible mode arguments for this option include the following\&.
435 .RS
436 .TP
437 always
438 Always generate a \f3package-info\&.class\fR file for every \f3package-info\&.java\fR file\&. This option may be useful if you use a build system such as Ant, which checks that each \f3\&.java\fR file has a corresponding \f3\&.class\fR file\&.
439 .TP
440 legacy
441 Generate a \f3package-info\&.class\fR file only if package-info\&.java contains annotations\&. Don\&'t generate a \f3package-info\&.class\fR file if package-info\&.java only contains comments\&.
442
443 \fINote:\fR A \f3package-info\&.class\fR file might be generated but be empty if all the annotations in the package-info\&.java file have \f3RetentionPolicy\&.SOURCE\fR\&.
444 .TP
445 nonempty
446 Generate a \f3package-info\&.class\fR file only if package-info\&.java contains annotations with \f3RetentionPolicy\&.CLASS\fR or \f3RetentionPolicy\&.RUNTIME\fR\&.
447 .RE
448
449 .TP
450 -Xprint
451 .br
452 Prints a textual representation of specified types for debugging purposes\&. Perform neither annotation processing nor compilation\&. The format of the output could change\&.
453 .TP
454 -XprintProcessorInfo
455 .br
456 Prints information about which annotations a processor is asked to process\&.
457 .TP
458 -XprintRounds
459 .br
460 Prints information about initial and subsequent annotation processing rounds\&.
461 .SH ENABLE\ OR\ DISABLE\ WARNINGS\ WITH\ THE\ -XLINT\ OPTION
462 Enable warning \fIname\fR with the \f3-Xlint:name\fR option, where \f3name\fR is one of the following warning names\&. Note that you can disable a warning with the \f3-Xlint:-name:\fR option\&.
463 .TP
464 cast
465 Warns about unnecessary and redundant casts, for example:
466 .sp
467 .nf
468 \f3String s = (String) "Hello!"\fP
469 .fi
470 .nf
471 \f3\fP
472 .fi
473 .sp
474
475 .TP
476 classfile
477 Warns about issues related to class file contents\&.
478 .TP
479 deprecation
480 Warns about the use of deprecated items, for example:
481 .sp
482 .nf
483 \f3java\&.util\&.Date myDate = new java\&.util\&.Date();\fP
484 .fi
485 .nf
486 \f3int currentDay = myDate\&.getDay();\fP
487 .fi
488 .nf
489 \f3\fP
490 .fi
491 .sp
492
493
494 The method \f3java\&.util\&.Date\&.getDay\fR has been deprecated since JDK 1\&.1
495 .TP
496 dep-ann
497 Warns about items that are documented with an \f3@deprecated\fR Javadoc comment, but do not have a \f3@Deprecated\fR annotation, for example:
498 .sp
499 .nf
500 \f3/**\fP
501 .fi
502 .nf
503 \f3 * @deprecated As of Java SE 7, replaced by {@link #newMethod()}\fP
504 .fi
505 .nf
506 \f3 */\fP
507 .fi
508 .nf
509 \f3public static void deprecatedMethood() { }\fP
510 .fi
511 .nf
512 \f3public static void newMethod() { }\fP
513 .fi
514 .nf
515 \f3\fP
516 .fi
517 .sp
518
519 .TP
520 divzero
521 Warns about division by the constant integer 0, for example:
522 .sp
523 .nf
524 \f3int divideByZero = 42 / 0;\fP
525 .fi
526 .nf
527 \f3\fP
528 .fi
529 .sp
530
531 .TP
532 empty
533 Warns about empty statements after \f3if\fRstatements, for example:
534 .sp
535 .nf
536 \f3class E {\fP
537 .fi
538 .nf
539 \f3 void m() {\fP
540 .fi
541 .nf
542 \f3 if (true) ;\fP
543 .fi
544 .nf
545 \f3 }\fP
546 .fi
547 .nf
548 \f3}\fP
549 .fi
550 .nf
551 \f3\fP
552 .fi
553 .sp
554
555 .TP
556 fallthrough
557 Checks the switch blocks for fall-through cases and provides a warning message for any that are found\&. Fall-through cases are cases in a switch block, other than the last case in the block, whose code does not include a break statement, allowing code execution to fall through from that case to the next case\&. For example, the code following the case 1 label in this switch block does not end with a break statement:
558 .sp
559 .nf
560 \f3switch (x) {\fP
561 .fi
562 .nf
563 \f3case 1:\fP
564 .fi
565 .nf
566 \f3 System\&.out\&.println("1");\fP
567 .fi
568 .nf
569 \f3 // No break statement here\&.\fP
570 .fi
571 .nf
572 \f3case 2:\fP
573 .fi
574 .nf
575 \f3 System\&.out\&.println("2");\fP
576 .fi
577 .nf
578 \f3}\fP
579 .fi
580 .nf
581 \f3\fP
582 .fi
583 .sp
584
585
586 If the \f3-Xlint:fallthrough\fR option was used when compiling this code, then the compiler emits a warning about possible fall-through into case, with the line number of the case in question\&.
587 .TP
588 finally
589 Warns about \f3finally\fR clauses that cannot complete normally, for example:
590 .sp
591 .nf
592 \f3public static int m() {\fP
593 .fi
594 .nf
595 \f3 try {\fP
596 .fi
597 .nf
598 \f3 throw new NullPointerException();\fP
599 .fi
600 .nf
601 \f3 } catch (NullPointerException(); {\fP
602 .fi
603 .nf
604 \f3 System\&.err\&.println("Caught NullPointerException\&.");\fP
605 .fi
606 .nf
607 \f3 return 1;\fP
608 .fi
609 .nf
610 \f3 } finally {\fP
611 .fi
612 .nf
613 \f3 return 0;\fP
614 .fi
615 .nf
616 \f3 }\fP
617 .fi
618 .nf
619 \f3 }\fP
620 .fi
621 .nf
622 \f3\fP
623 .fi
624 .sp
625
626
627 The compiler generates a warning for the \f3finally\fR block in this example\&. When the \f3int\fR method is called, it returns a value of 0\&. A \f3finally\fR block executes when the \f3try\fR block exits\&. In this example, when control is transferred to the \f3catch\fR block, the \f3int\fR method exits\&. However, the \f3finally\fR block must execute, so it is executed, even though control was transferred outside the method\&.
628 .TP
629 options
630 Warns about issues that related to the use of command-line options\&. See Cross-Compilation Options\&.
631 .TP
632 overrides
633 Warns about issues regarding method overrides\&. For example, consider the following two classes:
634 .sp
635 .nf
636 \f3public class ClassWithVarargsMethod {\fP
637 .fi
638 .nf
639 \f3 void varargsMethod(String\&.\&.\&. s) { }\fP
640 .fi
641 .nf
642 \f3}\fP
643 .fi
644 .nf
645 \f3\fP
646 .fi
647 .nf
648 \f3public class ClassWithOverridingMethod extends ClassWithVarargsMethod {\fP
649 .fi
650 .nf
651 \f3 @Override\fP
652 .fi
653 .nf
654 \f3 void varargsMethod(String[] s) { }\fP
655 .fi
656 .nf
657 \f3}\fP
658 .fi
659 .nf
660 \f3\fP
661 .fi
662 .sp
663
664
665 The compiler generates a warning similar to the following:\&.
666 .sp
667 .nf
668 \f3warning: [override] varargsMethod(String[]) in ClassWithOverridingMethod \fP
669 .fi
670 .nf
671 \f3overrides varargsMethod(String\&.\&.\&.) in ClassWithVarargsMethod; overriding\fP
672 .fi
673 .nf
674 \f3method is missing \&'\&.\&.\&.\&'\fP
675 .fi
676 .nf
677 \f3\fP
678 .fi
679 .sp
680
681
682 When the compiler encounters a \f3varargs\fR method, it translates the \f3varargs\fR formal parameter into an array\&. In the method \f3ClassWithVarargsMethod\&.varargsMethod\fR, the compiler translates the \f3varargs\fR formal parameter \f3String\&.\&.\&. s\fR to the formal parameter \f3String[] s\fR, an array, which matches the formal parameter of the method \f3ClassWithOverridingMethod\&.varargsMethod\fR\&. Consequently, this example compiles\&.
683 .TP
684 path
685 Warns about invalid path elements and nonexistent path directories on the command line (with regard to the class path, the source path, and other paths)\&. Such warnings cannot be suppressed with the \f3@SuppressWarnings\fR annotation, for example:
686 .sp
687 .nf
688 \f3javac \-Xlint:path \-classpath /nonexistentpath Example\&.java\fP
689 .fi
690 .nf
691 \f3\fP
692 .fi
693 .sp
694
695 .TP
696 processing
697 Warn about issues regarding annotation processing\&. The compiler generates this warning when you have a class that has an annotation, and you use an annotation processor that cannot handle that type of exception\&. For example, the following is a simple annotation processor:
698
699 \fISource file AnnocProc\&.java\fR:
700 .sp
701 .nf
702 \f3import java\&.util\&.*;\fP
703 .fi
704 .nf
705 \f3import javax\&.annotation\&.processing\&.*;\fP
706 .fi
707 .nf
708 \f3import javax\&.lang\&.model\&.*;\fP
709 .fi
710 .nf
711 \f3import\&.javaz\&.lang\&.model\&.element\&.*;\fP
712 .fi
713 .nf
714 \f3\fP
715 .fi
716 .nf
717 \f3@SupportedAnnotationTypes("NotAnno")\fP
718 .fi
719 .nf
720 \f3public class AnnoProc extends AbstractProcessor {\fP
721 .fi
722 .nf
723 \f3 public boolean process(Set<? extends TypeElement> elems, RoundEnvironment renv){\fP
724 .fi
725 .nf
726 \f3 return true;\fP
727 .fi
728 .nf
729 \f3 }\fP
730 .fi
731 .nf
732 \f3\fP
733 .fi
734 .nf
735 \f3 public SourceVersion getSupportedSourceVersion() {\fP
736 .fi
737 .nf
738 \f3 return SourceVersion\&.latest();\fP
739 .fi
740 .nf
741 \f3 }\fP
742 .fi
743 .nf
744 \f3}\fP
745 .fi
746 .nf
747 \f3\fP
748 .fi
749 .sp
750
751
752 \fISource file AnnosWithoutProcessors\&.java\fR:
753 .sp
754 .nf
755 \f3@interface Anno { }\fP
756 .fi
757 .nf
758 \f3\fP
759 .fi
760 .nf
761 \f3@Anno\fP
762 .fi
763 .nf
764 \f3class AnnosWithoutProcessors { }\fP
765 .fi
766 .nf
767 \f3\fP
768 .fi
769 .sp
770
771
772 The following commands compile the annotation processor \f3AnnoProc\fR, then run this annotation processor against the source file \f3AnnosWithoutProcessors\&.java\fR:
773 .sp
774 .nf
775 \f3javac AnnoProc\&.java\fP
776 .fi
777 .nf
778 \f3javac \-cp \&. \-Xlint:processing \-processor AnnoProc \-proc:only AnnosWithoutProcessors\&.java\fP
779 .fi
780 .nf
781 \f3\fP
782 .fi
783 .sp
784
785
786 When the compiler runs the annotation processor against the source file \f3AnnosWithoutProcessors\&.java\fR, it generates the following warning:
787 .sp
788 .nf
789 \f3warning: [processing] No processor claimed any of these annotations: Anno\fP
790 .fi
791 .nf
792 \f3\fP
793 .fi
794 .sp
795
796
797 To resolve this issue, you can rename the annotation defined and used in the class \f3AnnosWithoutProcessors\fR from \f3Anno\fR to \f3NotAnno\fR\&.
798 .TP
799 rawtypes
800 Warns about unchecked operations on raw types\&. The following statement generates a \f3rawtypes\fR warning:
801 .sp
802 .nf
803 \f3void countElements(List l) { \&.\&.\&. }\fP
804 .fi
805 .nf
806 \f3\fP
807 .fi
808 .sp
809
810
811 The following example does not generate a \f3rawtypes\fR warning
812 .sp
813 .nf
814 \f3void countElements(List<?> l) { \&.\&.\&. }\fP
815 .fi
816 .nf
817 \f3\fP
818 .fi
819 .sp
820
821
822 \f3List\fR is a raw type\&. However, \f3List<?>\fR is an unbounded wildcard parameterized type\&. Because \f3List\fR is a parameterized interface, always specify its type argument\&. In this example, the \f3List\fR formal argument is specified with an unbounded wildcard (\f3?\fR) as its formal type parameter, which means that the \f3countElements\fR method can accept any instantiation of the \f3List\fR interface\&.
823 .TP
824 Serial
825 Warns about missing \f3serialVersionUID\fR definitions on serializable classes, for example:
826 .sp
827 .nf
828 \f3public class PersistentTime implements Serializable\fP
829 .fi
830 .nf
831 \f3{\fP
832 .fi
833 .nf
834 \f3 private Date time;\fP
835 .fi
836 .nf
837 \f3\fP
838 .fi
839 .nf
840 \f3 public PersistentTime() {\fP
841 .fi
842 .nf
843 \f3 time = Calendar\&.getInstance()\&.getTime();\fP
844 .fi
845 .nf
846 \f3 }\fP
847 .fi
848 .nf
849 \f3\fP
850 .fi
851 .nf
852 \f3 public Date getTime() {\fP
853 .fi
854 .nf
855 \f3 return time;\fP
856 .fi
857 .nf
858 \f3 }\fP
859 .fi
860 .nf
861 \f3}\fP
862 .fi
863 .nf
864 \f3\fP
865 .fi
866 .sp
867
868
869 The compiler generates the following warning:
870 .sp
871 .nf
872 \f3warning: [serial] serializable class PersistentTime has no definition of\fP
873 .fi
874 .nf
875 \f3serialVersionUID\fP
876 .fi
877 .nf
878 \f3\fP
879 .fi
880 .sp
881
882
883 If a serializable class does not explicitly declare a field named \f3serialVersionUID\fR, then the serialization runtime environment calculates a default \f3serialVersionUID\fR value for that class based on various aspects of the class, as described in the Java Object Serialization Specification\&. However, it is strongly recommended that all serializable classes explicitly declare \f3serialVersionUID\fR values because the default process of computing \f3serialVersionUID\fR vales is highly sensitive to class details that can vary depending on compiler implementations, and as a result, might cause an unexpected \f3InvalidClassExceptions\fR during deserialization\&. To guarantee a consistent \f3serialVersionUID\fR value across different Java compiler implementations, a serializable class must declare an explicit \f3serialVersionUID\fR value\&.
884 .TP
885 static
886 Warns about issues relating to the use of statics, for example:
887 .sp
888 .nf
889 \f3class XLintStatic {\fP
890 .fi
891 .nf
892 \f3 static void m1() { }\fP
893 .fi
894 .nf
895 \f3 void m2() { this\&.m1(); }\fP
896 .fi
897 .nf
898 \f3}\fP
899 .fi
900 .nf
901 \f3\fP
902 .fi
903 .sp
904
905
906 The compiler generates the following warning:
907 .sp
908 .nf
909 \f3warning: [static] static method should be qualified by type name, \fP
910 .fi
911 .nf
912 \f3XLintStatic, instead of by an expression\fP
913 .fi
914 .nf
915 \f3\fP
916 .fi
917 .sp
918
919
920 To resolve this issue, you can call the \f3static\fR method \f3m1\fR as follows:
921 .sp
922 .nf
923 \f3XLintStatic\&.m1();\fP
924 .fi
925 .nf
926 \f3\fP
927 .fi
928 .sp
929
930
931 Alternately, you can remove the \f3static\fR keyword from the declaration of the method \f3m1\fR\&.
932 .TP
933 try
934 Warns about issues relating to use of \f3try\fR blocks, including try-with-resources statements\&. For example, a warning is generated for the following statement because the resource \f3ac\fR declared in the \f3try\fR block is not used:
935 .sp
936 .nf
937 \f3try ( AutoCloseable ac = getResource() ) { // do nothing}\fP
938 .fi
939 .nf
940 \f3\fP
941 .fi
942 .sp
943
944 .TP
945 unchecked
946 Gives more detail for unchecked conversion warnings that are mandated by the Java Language Specification, for example:
947 .sp
948 .nf
949 \f3List l = new ArrayList<Number>();\fP
950 .fi
951 .nf
952 \f3List<String> ls = l; // unchecked warning\fP
953 .fi
954 .nf
955 \f3\fP
956 .fi
957 .sp
958
959
960 During type erasure, the types \f3ArrayList<Number>\fR and \f3List<String>\fR become \f3ArrayList\fR and \f3List\fR, respectively\&.
961
962 The \f3ls\fR command has the parameterized type \f3List<String>\fR\&. When the \f3List\fR referenced by \f3l\fR is assigned to \f3ls\fR, the compiler generates an unchecked warning\&. At compile time, the compiler and JVM cannot determine whether \f3l\fR refers to a \f3List<String>\fR type\&. In this case, \f3l\fR does not refer to a \f3List<String>\fR type\&. As a result, heap pollution occurs\&.
963
964 A heap pollution situation occurs when the \f3List\fR object \f3l\fR, whose static type is \f3List<Number>\fR, is assigned to another \f3List\fR object, \f3ls\fR, that has a different static type, \f3List<String>\fR\&. However, the compiler still allows this assignment\&. It must allow this assignment to preserve backward compatibility with releases of Java SE that do not support generics\&. Because of type erasure, \f3List<Number>\fR and \f3List<String>\fR both become \f3List\fR\&. Consequently, the compiler allows the assignment of the object \f3l\fR\f3,\fR which has a raw type of \f3List\fR, to the object \f3ls\fR\&.
965 .TP
966 varargs
967 Warns about unsafe usages of variable arguments (\f3varargs\fR) methods, in particular, those that contain non-reifiable arguments, for example:
968 .sp
969 .nf
970 \f3public class ArrayBuilder {\fP
971 .fi
972 .nf
973 \f3 public static <T> void addToList (List<T> listArg, T\&.\&.\&. elements) {\fP
974 .fi
975 .nf
976 \f3 for (T x : elements) {\fP
977 .fi
978 .nf
979 \f3 listArg\&.add(x);\fP
980 .fi
981 .nf
982 \f3 }\fP
983 .fi
984 .nf
985 \f3 }\fP
986 .fi
987 .nf
988 \f3}\fP
989 .fi
990 .nf
991 \f3\fP
992 .fi
993 .sp
994
995
996 \fINote:\fR A non-reifiable type is a type whose type information is not fully available at runtime\&.
997
998 The compiler generates the following warning for the definition of the method \f3ArrayBuilder\&.addToList\fR
999 .sp
1000 .nf
1001 \f3warning: [varargs] Possible heap pollution from parameterized vararg type T\fP
1002 .fi
1003 .nf
1004 \f3\fP
1005 .fi
1006 .sp
1007
1008
1009 When the compiler encounters a varargs method, it translates the \f3varargs\fR formal parameter into an array\&. However, the Java programming language does not permit the creation of arrays of parameterized types\&. In the method \f3ArrayBuilder\&.addToList\fR, the compiler translates the \f3varargs\fR formal parameter \f3T\&.\&.\&.\fR elements to the formal parameter \f3T[]\fR elements, an array\&. However, because of type erasure, the compiler converts the \f3varargs\fR formal parameter to \f3Object[]\fR elements\&. Consequently, there is a possibility of heap pollution\&.
1010 .SH COMMAND-LINE\ ARGUMENT\ FILES
1011 To shorten or simplify the \f3javac\fR command, you can specify one or more files that contain arguments to the \f3javac\fR command (except \f3-J\fR options)\&. This enables you to create \f3javac\fR commands of any length on any operating system\&.
1012 .PP
1013 An argument file can include \f3javac\fR options and source file names in any combination\&. The arguments within a file can be separated by spaces or new line characters\&. If a file name contains embedded spaces, then put the whole file name in double quotation marks\&.
1014 .PP
1015 File Names within an argument file are relative to the current directory, not the location of the argument file\&. Wild cards (*) are not allowed in these lists (such as for specifying \f3*\&.java\fR)\&. Use of the at sign (@) to recursively interpret files is not supported\&. The \f3-J\fR options are not supported because they are passed to the launcher, which does not support argument files\&.
1016 .PP
1017 When executing the \f3javac\fR command, pass in the path and name of each argument file with the at sign (@) leading character\&. When the \f3javac\fR command encounters an argument beginning with the at sign (@), it expands the contents of that file into the argument list\&.
1018 .PP
1019 \f3Example 1 Single Argument File\fR
1020 .PP
1021 You could use a single argument file named \f3argfile\fR to hold all \f3javac\fR arguments:
1022 .sp
1023 .nf
1024 \f3javac @argfile\fP
1025 .fi
1026 .nf
1027 \f3\fP
1028 .fi
1029 .sp
1030 This argument file could contain the contents of both files shown in Example 2
1031 .PP
1032 \f3Example 2 Two Argument Files\fR
1033 .PP
1034 You can create two argument files: one for the \f3javac\fR options and the other for the source file names\&. Note that the following lists have no line-continuation characters\&.
1035 .PP
1036 Create a file named options that contains the following:
1037 .sp
1038 .nf
1039 \f3\-d classes\fP
1040 .fi
1041 .nf
1042 \f3\-g\fP
1043 .fi
1044 .nf
1045 \f3\-sourcepath /java/pubs/ws/1\&.3/src/share/classes\fP
1046 .fi
1047 .nf
1048 \f3\fP
1049 .fi
1050 .sp
1051 Create a file named classes that contains the following:
1052 .sp
1053 .nf
1054 \f3MyClass1\&.java\fP
1055 .fi
1056 .nf
1057 \f3MyClass2\&.java\fP
1058 .fi
1059 .nf
1060 \f3MyClass3\&.java\fP
1061 .fi
1062 .nf
1063 \f3\fP
1064 .fi
1065 .sp
1066 Then, run the \f3javac\fR command as follows:
1067 .sp
1068 .nf
1069 \f3javac @options @classes\fP
1070 .fi
1071 .nf
1072 \f3\fP
1073 .fi
1074 .sp
1075 \f3Example 3 Argument Files with Paths\fR
1076 .PP
1077 The argument files can have paths, but any file names inside the files are relative to the current working directory (not \f3path1\fR or \f3path2\fR):
1078 .sp
1079 .nf
1080 \f3javac @path1/options @path2/classes\fP
1081 .fi
1082 .nf
1083 \f3\fP
1084 .fi
1085 .sp
1086 .SH ANNOTATION\ PROCESSING
1087 The \f3javac\fR command provides direct support for annotation processing, superseding the need for the separate annotation processing command, \f3apt\fR\&.
1088 .PP
1089 The API for annotation processors is defined in the \f3javax\&.annotation\&.processing\fR and j\f3avax\&.lang\&.model\fR packages and subpackages\&.
1090 .SS HOW\ ANNOTATION\ PROCESSING\ WORKS
1091 Unless annotation processing is disabled with the \f3-proc:none\fR option, the compiler searches for any annotation processors that are available\&. The search path can be specified with the \f3-processorpath\fR option\&. If no path is specified, then the user class path is used\&. Processors are located by means of service provider-configuration files named \f3META-INF/services/javax\&.annotation\&.processing\fR\&.Processor on the search path\&. Such files should contain the names of any annotation processors to be used, listed one per line\&. Alternatively, processors can be specified explicitly, using the \f3-processor\fR option\&.
1092 .PP
1093 After scanning the source files and classes on the command line to determine what annotations are present, the compiler queries the processors to determine what annotations they process\&. When a match is found, the processor is called\&. A processor can claim the annotations it processes, in which case no further attempt is made to find any processors for those annotations\&. After all of the annotations are claimed, the compiler does not search for additional processors\&.
1094 .PP
1095 If any processors generate new source files, then another round of annotation processing occurs: Any newly generated source files are scanned, and the annotations processed as before\&. Any processors called on previous rounds are also called on all subsequent rounds\&. This continues until no new source files are generated\&.
1096 .PP
1097 After a round occurs where no new source files are generated, the annotation processors are called one last time, to give them a chance to complete any remaining work\&. Finally, unless the \f3-proc:only\fR option is used, the compiler compiles the original and all generated source files\&.
1098 .SS IMPLICITLY\ LOADED\ SOURCE\ FILES
1099 To compile a set of source files, the compiler might need to implicitly load additional source files\&. See Searching for Types\&. Such files are currently not subject to annotation processing\&. By default, the compiler gives a warning when annotation processing occurred and any implicitly loaded source files are compiled\&. The \f3-implicit\fR option provides a way to suppress the warning\&.
1100 .SH SEARCHING\ FOR\ TYPES
1101 To compile a source file, the compiler often needs information about a type, but the type definition is not in the source files specified on the command line\&. The compiler needs type information for every class or interface used, extended, or implemented in the source file\&. This includes classes and interfaces not explicitly mentioned in the source file, but that provide information through inheritance\&.
1102 .PP
1103 For example, when you create a subclass \f3java\&.applet\&.Applet\fR, you are also using the ancestor classes of \f3Applet\fR: \f3java\&.awt\&.Panel\fR, \f3java\&.awt\&.Container\fR, \f3java\&.awt\&.Component\fR, and \f3java\&.lang\&.Object\fR\&.
1104 .PP
1105 When the compiler needs type information, it searches for a source file or class file that defines the type\&. The compiler searches for class files first in the bootstrap and extension classes, then in the user class path (which by default is the current directory)\&. The user class path is defined by setting the \f3CLASSPATH\fR environment variable or by using the \f3-classpath\fR option\&.
1106 .PP
1107 If you set the \f3-sourcepath\fR option, then the compiler searches the indicated path for source files\&. Otherwise, the compiler searches the user class path for both class files and source files\&.
1108 .PP
1109 You can specify different bootstrap or extension classes with the \f3-bootclasspath\fR and the \f3-extdirs\fR options\&. See Cross-Compilation Options\&.
1110 .PP
1111 A successful type search may produce a class file, a source file, or both\&. If both are found, then you can use the \f3-Xprefer\fR option to instruct the compiler which to use\&. If \f3newer\fR is specified, then the compiler uses the newer of the two files\&. If \f3source\fR is specified, the compiler uses the source file\&. The default is \f3newer\fR\&.
1112 .PP
1113 If a type search finds a source file for a required type, either by itself, or as a result of the setting for the \f3-Xprefer\fR option, then the compiler reads the source file to get the information it needs\&. By default the compiler also compiles the source file\&. You can use the \f3-implicit\fR option to specify the behavior\&. If \f3none\fR is specified, then no class files are generated for the source file\&. If \f3class\fR is specified, then class files are generated for the source file\&.
1114 .PP
1115 The compiler might not discover the need for some type information until after annotation processing completes\&. When the type information is found in a source file and no \f3-implicit\fR option is specified, the compiler gives a warning that the file is being compiled without being subject to annotation processing\&. To disable the warning, either specify the file on the command line (so that it will be subject to annotation processing) or use the \f3-implicit\fR option to specify whether or not class files should be generated for such source files\&.
1116 .SH PROGRAMMATIC\ INTERFACE
1117 The \f3javac\fR command supports the new Java Compiler API defined by the classes and interfaces in the \f3javax\&.tools\fR package\&.
1118 .SS EXAMPLE
1119 To compile as though providing command-line arguments, use the following syntax:
1120 .sp
1121 .nf
1122 \f3JavaCompiler javac = ToolProvider\&.getSystemJavaCompiler();\fP
1123 .fi
1124 .nf
1125 \f3\fP
1126 .fi
1127 .sp
1128 The example writes diagnostics to the standard output stream and returns the exit code that \f3javac\fR would give when called from the command line\&.
1129 .PP
1130 You can use other methods in the \f3javax\&.tools\&.JavaCompiler\fR interface to handle diagnostics, control where files are read from and written to, and more\&.
1131 .SS OLD\ INTERFACE
1132 \fINote:\fR This API is retained for backward compatibility only\&. All new code should use the newer Java Compiler API\&.
1133 .PP
1134 The \f3com\&.sun\&.tools\&.javac\&.Main\fR class provides two static methods to call the compiler from a program:
1135 .sp
1136 .nf
1137 \f3public static int compile(String[] args);\fP
1138 .fi
1139 .nf
1140 \f3public static int compile(String[] args, PrintWriter out);\fP
1141 .fi
1142 .nf
1143 \f3\fP
1144 .fi
1145 .sp
1146 The \f3args\fR parameter represents any of the command-line arguments that would typically be passed to the compiler\&.
1147 .PP
1148 The \f3out\fR parameter indicates where the compiler diagnostic output is directed\&.
1149 .PP
1150 The \f3return\fR value is equivalent to the \f3exit\fR value from \f3javac\fR\&.
1151 .PP
1152 \fINote:\fR All other classes and methods found in a package with names that start with \f3com\&.sun\&.tools\&.javac\fR (subpackages of \f3com\&.sun\&.tools\&.javac\fR) are strictly internal and subject to change at any time\&.
1153 .SH EXAMPLES
1154 \f3Example 1 Compile a Simple Program\fR
1155 .PP
1156 This example shows how to compile the \f3Hello\&.java\fR source file in the greetings directory\&. The class defined in \f3Hello\&.java\fR is called \f3greetings\&.Hello\fR\&. The greetings directory is the package directory both for the source file and the class file and is underneath the current directory\&. This makes it possible to use the default user class path\&. It also makes it unnecessary to specify a separate destination directory with the \f3-d\fR option\&.
1157 .PP
1158 The source code in \f3Hello\&.java\fR:
1159 .sp
1160 .nf
1161 \f3package greetings;\fP
1162 .fi
1163 .nf
1164 \f3\fP
1165 .fi
1166 .nf
1167 \f3public class Hello {\fP
1168 .fi
1169 .nf
1170 \f3 public static void main(String[] args) {\fP
1171 .fi
1172 .nf
1173 \f3 for (int i=0; i < args\&.length; i++) {\fP
1174 .fi
1175 .nf
1176 \f3 System\&.out\&.println("Hello " + args[i]);\fP
1177 .fi
1178 .nf
1179 \f3 }\fP
1180 .fi
1181 .nf
1182 \f3 }\fP
1183 .fi
1184 .nf
1185 \f3}\fP
1186 .fi
1187 .nf
1188 \f3\fP
1189 .fi
1190 .sp
1191 Compile greetings\&.Hello:
1192 .sp
1193 .nf
1194 \f3javac greetings/Hello\&.java\fP
1195 .fi
1196 .nf
1197 \f3\fP
1198 .fi
1199 .sp
1200 Run \f3greetings\&.Hello\fR:
1201 .sp
1202 .nf
1203 \f3java greetings\&.Hello World Universe Everyone\fP
1204 .fi
1205 .nf
1206 \f3Hello World\fP
1207 .fi
1208 .nf
1209 \f3Hello Universe\fP
1210 .fi
1211 .nf
1212 \f3Hello Everyone\fP
1213 .fi
1214 .nf
1215 \f3\fP
1216 .fi
1217 .sp
1218 \f3Example 2 Compile Multiple Source Files\fR
1219 .PP
1220 This example compiles the \f3Aloha\&.java\fR, \f3GutenTag\&.java\fR, \f3Hello\&.java\fR, and \f3Hi\&.java\fR source files in the \f3greetings\fR package\&.
1221 .sp
1222 .nf
1223 \f3% javac greetings/*\&.java\fP
1224 .fi
1225 .nf
1226 \f3% ls greetings\fP
1227 .fi
1228 .nf
1229 \f3Aloha\&.class GutenTag\&.class Hello\&.class Hi\&.class\fP
1230 .fi
1231 .nf
1232 \f3Aloha\&.java GutenTag\&.java Hello\&.java Hi\&.java\fP
1233 .fi
1234 .nf
1235 \f3\fP
1236 .fi
1237 .sp
1238 \f3Example 3 Specify a User Class Path\fR
1239 .PP
1240 After changing one of the source files in the previous example, recompile it:
1241 .sp
1242 .nf
1243 \f3pwd\fP
1244 .fi
1245 .nf
1246 \f3/examples\fP
1247 .fi
1248 .nf
1249 \f3javac greetings/Hi\&.java\fP
1250 .fi
1251 .nf
1252 \f3\fP
1253 .fi
1254 .sp
1255 Because \f3greetings\&.Hi\fR refers to other classes in the \f3greetings\fR package, the compiler needs to find these other classes\&. The previous example works because the default user class path is the directory that contains the package directory\&. If you want to recompile this file without concern for which directory you are in, then add the examples directory to the user class path by setting \f3CLASSPATH\fR\&. This example uses the \f3-classpath\fR option\&.
1256 .sp
1257 .nf
1258 \f3javac \-classpath /examples /examples/greetings/Hi\&.java\fP
1259 .fi
1260 .nf
1261 \f3\fP
1262 .fi
1263 .sp
1264 If you change \f3greetings\&.Hi\fR to use a banner utility, then that utility also needs to be accessible through the user class path\&.
1265 .sp
1266 .nf
1267 \f3javac \-classpath /examples:/lib/Banners\&.jar \e\fP
1268 .fi
1269 .nf
1270 \f3 /examples/greetings/Hi\&.java\fP
1271 .fi
1272 .nf
1273 \f3\fP
1274 .fi
1275 .sp
1276 To execute a class in the \f3greetings\fR package, the program needs access to the \f3greetings\fR package, and to the classes that the \f3greetings\fR classes use\&.
1277 .sp
1278 .nf
1279 \f3java \-classpath /examples:/lib/Banners\&.jar greetings\&.Hi\fP
1280 .fi
1281 .nf
1282 \f3\fP
1283 .fi
1284 .sp
1285 \f3Example 4 Separate Source Files and Class Files\fR
1286 .PP
1287 The following example uses \f3javac\fR to compile code that runs on JVM 1\&.7\&.
1288 .sp
1289 .nf
1290 \f3javac \-source 1\&.7 \-target 1\&.7 \-bootclasspath jdk1\&.7\&.0/lib/rt\&.jar \e \fP
1291 .fi
1292 .nf
1293 \f3\-extdirs "" OldCode\&.java\fP
1294 .fi
1295 .nf
1296 \f3\fP
1297 .fi
1298 .sp
1299 The \f3-source 1\&.7\fR option specifies that release 1\&.7 (or 7) of the Java programming language be used to compile \f3OldCode\&.java\fR\&. The option \f3-target 1\&.7\fR option ensures that the generated class files are compatible with JVM 1\&.7\&. Note that in most cases, the value of the \f3-target\fR option is the value of the \f3-source\fR option; in this example, you can omit the \f3-target\fR option\&.
1300 .PP
1301 You must specify the \f3-bootclasspath\fR option to specify the correct version of the bootstrap classes (the \f3rt\&.jar\fR library)\&. If not, then the compiler generates a warning:
1302 .sp
1303 .nf
1304 \f3javac \-source 1\&.7 OldCode\&.java\fP
1305 .fi
1306 .nf
1307 \f3warning: [options] bootstrap class path not set in conjunction with \fP
1308 .fi
1309 .nf
1310 \f3\-source 1\&.7\fP
1311 .fi
1312 .nf
1313 \f3\fP
1314 .fi
1315 .sp
1316 If you do not specify the correct version of bootstrap classes, then the compiler uses the old language rules (in this example, it uses version 1\&.7 of the Java programming language) combined with the new bootstrap classes, which can result in class files that do not work on the older platform (in this case, Java SE 7) because reference to nonexistent methods can get included\&.
1317 .PP
1318 \f3Example 5 Cross Compile\fR
1319 .PP
1320 This example uses \f3javac\fR to compile code that runs on JVM 1\&.7\&.
1321 .sp
1322 .nf
1323 \f3javac \-source 1\&.7 \-target 1\&.7 \-bootclasspath jdk1\&.7\&.0/lib/rt\&.jar \e\fP
1324 .fi
1325 .nf
1326 \f3 \-extdirs "" OldCode\&.java\fP
1327 .fi
1328 .nf
1329 \f3\fP
1330 .fi
1331 .sp
1332 The\f3-source 1\&.7\fR option specifies that release 1\&.7 (or 7) of the Java programming language to be used to compile OldCode\&.java\&. The \f3-target 1\&.7\fR option ensures that the generated class files are compatible with JVM 1\&.7\&.
1333 .PP
1334 You must specify the \f3-bootclasspath\fR option to specify the correct version of the bootstrap classes (the \f3rt\&.jar\fR library)\&. If not, then the compiler generates a warning:
1335 .sp
1336 .nf
1337 \f3javac \-source 1\&.7 OldCode\&.java\fP
1338 .fi
1339 .nf
1340 \f3warning: [options] bootstrap class path not set in conjunction with \-source 1\&.7\fP
1341 .fi
1342 .nf
1343 \f3\fP
1344 .fi
1345 .sp
1346 If you do not specify the correct version of bootstrap classes, then the compiler uses the old language rules combined with the new bootstrap classes\&. This combination can result in class files that do not work on the older platform (in this case, Java SE 7) because reference to nonexistent methods can get included\&. In this example, the compiler uses release 1\&.7 of the Java programming language\&.
1347 .SH SEE\ ALSO
1348 .TP 0.2i
1349 \(bu
1350 java(1)
1351 .TP 0.2i
1352 \(bu
1353 jdb(1)
1354 .TP 0.2i
1355 \(bu
1356 javadoc(1)
1357 .TP 0.2i
1358 \(bu
1359 jar(1)
1360 .TP 0.2i
1361 \(bu
1362 jdb(1)
1363 .RE
1364 .br
1365 'pl 8.5i
1366 'bp