Unlike the {@link PrintStream} class, if automatic flushing is enabled * it will be done only when one of the println, printf, or * format methods is invoked, rather than whenever a newline character * happens to be output. These methods use the platform's own notion of line * separator rather than the newline character. * *
Methods in this class never throw I/O exceptions, although some of its
* constructors may. The client may inquire as to whether any errors have
* occurred by invoking {@link #checkError checkError()}.
*
* @author Frank Yellin
* @author Mark Reinhold
* @since 1.1
*/
public class PrintWriter extends Writer {
/**
* The underlying character-output stream of this
* PrintWriter.
*
* @since 1.2
*/
protected Writer out;
private final boolean autoFlush;
private boolean trouble = false;
private Formatter formatter;
private PrintStream psOut = null;
/**
* Line separator string. This is the value of the line.separator
* property at the moment that the stream was created.
*/
private final String lineSeparator;
/**
* Returns a charset object for the given charset name.
* @throws NullPointerException is csn is null
* @throws UnsupportedEncodingException if the charset is not supported
*/
private static Charset toCharset(String csn)
throws UnsupportedEncodingException
{
Objects.requireNonNull(csn, "charsetName");
try {
return Charset.forName(csn);
} catch (IllegalCharsetNameException|UnsupportedCharsetException unused) {
// UnsupportedEncodingException should be thrown
throw new UnsupportedEncodingException(csn);
}
}
/**
* Creates a new PrintWriter, without automatic line flushing.
*
* @param out A character-output stream
*/
public PrintWriter (Writer out) {
this(out, false);
}
/**
* Creates a new PrintWriter.
*
* @param out A character-output stream
* @param autoFlush A boolean; if true, the println,
* printf, or format methods will
* flush the output buffer
*/
public PrintWriter(Writer out,
boolean autoFlush) {
super(out);
this.out = out;
this.autoFlush = autoFlush;
lineSeparator = java.security.AccessController.doPrivileged(
new sun.security.action.GetPropertyAction("line.separator"));
}
/**
* Creates a new PrintWriter, without automatic line flushing, from an
* existing OutputStream. This convenience constructor creates the
* necessary intermediate OutputStreamWriter, which will convert characters
* into bytes using the default character encoding.
*
* @param out An output stream
*
* @see java.io.OutputStreamWriter#OutputStreamWriter(java.io.OutputStream)
*/
public PrintWriter(OutputStream out) {
this(out, false);
}
/**
* Creates a new PrintWriter from an existing OutputStream. This
* convenience constructor creates the necessary intermediate
* OutputStreamWriter, which will convert characters into bytes using the
* default character encoding.
*
* @param out An output stream
* @param autoFlush A boolean; if true, the println,
* printf, or format methods will
* flush the output buffer
*
* @see java.io.OutputStreamWriter#OutputStreamWriter(java.io.OutputStream)
*/
public PrintWriter(OutputStream out, boolean autoFlush) {
this(new BufferedWriter(new OutputStreamWriter(out)), autoFlush);
// save print stream for error propagation
if (out instanceof java.io.PrintStream) {
psOut = (PrintStream) out;
}
}
/**
* Creates a new PrintWriter, without automatic line flushing, with the
* specified file name. This convenience constructor creates the necessary
* intermediate {@link java.io.OutputStreamWriter OutputStreamWriter},
* which will encode characters using the {@linkplain
* java.nio.charset.Charset#defaultCharset() default charset} for this
* instance of the Java virtual machine.
*
* @param fileName
* The name of the file to use as the destination of this writer.
* If the file exists then it will be truncated to zero size;
* otherwise, a new file will be created. The output will be
* written to the file and is buffered.
*
* @throws FileNotFoundException
* If the given string does not denote an existing, writable
* regular file and a new regular file of that name cannot be
* created, or if some other error occurs while opening or
* creating the file
*
* @throws SecurityException
* If a security manager is present and {@link
* SecurityManager#checkWrite checkWrite(fileName)} denies write
* access to the file
*
* @since 1.5
*/
public PrintWriter(String fileName) throws FileNotFoundException {
this(new BufferedWriter(new OutputStreamWriter(new FileOutputStream(fileName))),
false);
}
/* Private constructor */
private PrintWriter(Charset charset, File file)
throws FileNotFoundException
{
this(new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), charset)),
false);
}
/**
* Creates a new PrintWriter, without automatic line flushing, with the
* specified file name and charset. This convenience constructor creates
* the necessary intermediate {@link java.io.OutputStreamWriter
* OutputStreamWriter}, which will encode characters using the provided
* charset.
*
* @param fileName
* The name of the file to use as the destination of this writer.
* If the file exists then it will be truncated to zero size;
* otherwise, a new file will be created. The output will be
* written to the file and is buffered.
*
* @param csn
* The name of a supported {@linkplain java.nio.charset.Charset
* charset}
*
* @throws FileNotFoundException
* If the given string does not denote an existing, writable
* regular file and a new regular file of that name cannot be
* created, or if some other error occurs while opening or
* creating the file
*
* @throws SecurityException
* If a security manager is present and {@link
* SecurityManager#checkWrite checkWrite(fileName)} denies write
* access to the file
*
* @throws UnsupportedEncodingException
* If the named charset is not supported
*
* @since 1.5
*/
public PrintWriter(String fileName, String csn)
throws FileNotFoundException, UnsupportedEncodingException
{
this(toCharset(csn), new File(fileName));
}
/**
* Creates a new PrintWriter, without automatic line flushing, with the
* specified file. This convenience constructor creates the necessary
* intermediate {@link java.io.OutputStreamWriter OutputStreamWriter},
* which will encode characters using the {@linkplain
* java.nio.charset.Charset#defaultCharset() default charset} for this
* instance of the Java virtual machine.
*
* @param file
* The file to use as the destination of this writer. If the file
* exists then it will be truncated to zero size; otherwise, a new
* file will be created. The output will be written to the file
* and is buffered.
*
* @throws FileNotFoundException
* If the given file object does not denote an existing, writable
* regular file and a new regular file of that name cannot be
* created, or if some other error occurs while opening or
* creating the file
*
* @throws SecurityException
* If a security manager is present and {@link
* SecurityManager#checkWrite checkWrite(file.getPath())}
* denies write access to the file
*
* @since 1.5
*/
public PrintWriter(File file) throws FileNotFoundException {
this(new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file))),
false);
}
/**
* Creates a new PrintWriter, without automatic line flushing, with the
* specified file and charset. This convenience constructor creates the
* necessary intermediate {@link java.io.OutputStreamWriter
* OutputStreamWriter}, which will encode characters using the provided
* charset.
*
* @param file
* The file to use as the destination of this writer. If the file
* exists then it will be truncated to zero size; otherwise, a new
* file will be created. The output will be written to the file
* and is buffered.
*
* @param csn
* The name of a supported {@linkplain java.nio.charset.Charset
* charset}
*
* @throws FileNotFoundException
* If the given file object does not denote an existing, writable
* regular file and a new regular file of that name cannot be
* created, or if some other error occurs while opening or
* creating the file
*
* @throws SecurityException
* If a security manager is present and {@link
* SecurityManager#checkWrite checkWrite(file.getPath())}
* denies write access to the file
*
* @throws UnsupportedEncodingException
* If the named charset is not supported
*
* @since 1.5
*/
public PrintWriter(File file, String csn)
throws FileNotFoundException, UnsupportedEncodingException
{
this(toCharset(csn), file);
}
/** Checks to make sure that the stream has not been closed */
private void ensureOpen() throws IOException {
if (out == null)
throw new IOException("Stream closed");
}
/**
* Flushes the stream.
* @see #checkError()
*/
public void flush() {
try {
synchronized (lock) {
ensureOpen();
out.flush();
}
}
catch (IOException x) {
trouble = true;
}
}
/**
* Closes the stream and releases any system resources associated
* with it. Closing a previously closed stream has no effect.
*
* @see #checkError()
*/
public void close() {
try {
synchronized (lock) {
if (out == null)
return;
out.close();
out = null;
}
}
catch (IOException x) {
trouble = true;
}
}
/**
* Flushes the stream if it's not closed and checks its error state.
*
* @return true if the print stream has encountered an error,
* either on the underlying output stream or during a format
* conversion.
*/
public boolean checkError() {
if (out != null) {
flush();
}
if (out instanceof java.io.PrintWriter) {
PrintWriter pw = (PrintWriter) out;
return pw.checkError();
} else if (psOut != null) {
return psOut.checkError();
}
return trouble;
}
/**
* Indicates that an error has occurred.
*
*
This method will cause subsequent invocations of {@link * #checkError()} to return true until {@link * #clearError()} is invoked. */ protected void setError() { trouble = true; } /** * Clears the error state of this stream. * *
This method will cause subsequent invocations of {@link
* #checkError()} to return false until another write
* operation fails and invokes {@link #setError()}.
*
* @since 1.6
*/
protected void clearError() {
trouble = false;
}
/*
* Exception-catching, synchronized output operations,
* which also implement the write() methods of Writer
*/
/**
* Writes a single character.
* @param c int specifying a character to be written.
*/
public void write(int c) {
try {
synchronized (lock) {
ensureOpen();
out.write(c);
}
}
catch (InterruptedIOException x) {
Thread.currentThread().interrupt();
}
catch (IOException x) {
trouble = true;
}
}
/**
* Writes A Portion of an array of characters.
* @param buf Array of characters
* @param off Offset from which to start writing characters
* @param len Number of characters to write
*/
public void write(char buf[], int off, int len) {
try {
synchronized (lock) {
ensureOpen();
out.write(buf, off, len);
}
}
catch (InterruptedIOException x) {
Thread.currentThread().interrupt();
}
catch (IOException x) {
trouble = true;
}
}
/**
* Writes an array of characters. This method cannot be inherited from the
* Writer class because it must suppress I/O exceptions.
* @param buf Array of characters to be written
*/
public void write(char buf[]) {
write(buf, 0, buf.length);
}
/**
* Writes a portion of a string.
* @param s A String
* @param off Offset from which to start writing characters
* @param len Number of characters to write
*/
public void write(String s, int off, int len) {
try {
synchronized (lock) {
ensureOpen();
out.write(s, off, len);
}
}
catch (InterruptedIOException x) {
Thread.currentThread().interrupt();
}
catch (IOException x) {
trouble = true;
}
}
/**
* Writes a string. This method cannot be inherited from the Writer class
* because it must suppress I/O exceptions.
* @param s String to be written
*/
public void write(String s) {
write(s, 0, s.length());
}
private void newLine() {
try {
synchronized (lock) {
ensureOpen();
out.write(lineSeparator);
if (autoFlush)
out.flush();
}
}
catch (InterruptedIOException x) {
Thread.currentThread().interrupt();
}
catch (IOException x) {
trouble = true;
}
}
/* Methods that do not terminate lines */
/**
* Prints a boolean value. The string produced by {@link
* java.lang.String#valueOf(boolean)} is translated into bytes
* according to the platform's default character encoding, and these bytes
* are written in exactly the manner of the {@link
* #write(int)} method.
*
* @param b The boolean to be printed
*/
public void print(boolean b) {
write(b ? "true" : "false");
}
/**
* Prints a character. The character is translated into one or more bytes
* according to the platform's default character encoding, and these bytes
* are written in exactly the manner of the {@link
* #write(int)} method.
*
* @param c The char to be printed
*/
public void print(char c) {
write(c);
}
/**
* Prints an integer. The string produced by {@link
* java.lang.String#valueOf(int)} is translated into bytes according
* to the platform's default character encoding, and these bytes are
* written in exactly the manner of the {@link #write(int)}
* method.
*
* @param i The int to be printed
* @see java.lang.Integer#toString(int)
*/
public void print(int i) {
write(String.valueOf(i));
}
/**
* Prints a long integer. The string produced by {@link
* java.lang.String#valueOf(long)} is translated into bytes
* according to the platform's default character encoding, and these bytes
* are written in exactly the manner of the {@link #write(int)}
* method.
*
* @param l The long to be printed
* @see java.lang.Long#toString(long)
*/
public void print(long l) {
write(String.valueOf(l));
}
/**
* Prints a floating-point number. The string produced by {@link
* java.lang.String#valueOf(float)} is translated into bytes
* according to the platform's default character encoding, and these bytes
* are written in exactly the manner of the {@link #write(int)}
* method.
*
* @param f The float to be printed
* @see java.lang.Float#toString(float)
*/
public void print(float f) {
write(String.valueOf(f));
}
/**
* Prints a double-precision floating-point number. The string produced by
* {@link java.lang.String#valueOf(double)} is translated into
* bytes according to the platform's default character encoding, and these
* bytes are written in exactly the manner of the {@link
* #write(int)} method.
*
* @param d The double to be printed
* @see java.lang.Double#toString(double)
*/
public void print(double d) {
write(String.valueOf(d));
}
/**
* Prints an array of characters. The characters are converted into bytes
* according to the platform's default character encoding, and these bytes
* are written in exactly the manner of the {@link #write(int)}
* method.
*
* @param s The array of chars to be printed
*
* @throws NullPointerException If s is null
*/
public void print(char s[]) {
write(s);
}
/**
* Prints a string. If the argument is null then the string
* "null" is printed. Otherwise, the string's characters are
* converted into bytes according to the platform's default character
* encoding, and these bytes are written in exactly the manner of the
* {@link #write(int)} method.
*
* @param s The String to be printed
*/
public void print(String s) {
if (s == null) {
s = "null";
}
write(s);
}
/**
* Prints an object. The string produced by the {@link
* java.lang.String#valueOf(Object)} method is translated into bytes
* according to the platform's default character encoding, and these bytes
* are written in exactly the manner of the {@link #write(int)}
* method.
*
* @param obj The Object to be printed
* @see java.lang.Object#toString()
*/
public void print(Object obj) {
write(String.valueOf(obj));
}
/* Methods that do terminate lines */
/**
* Terminates the current line by writing the line separator string. The
* line separator string is defined by the system property
* line.separator, and is not necessarily a single newline
* character ('\n').
*/
public void println() {
newLine();
}
/**
* Prints a boolean value and then terminates the line. This method behaves
* as though it invokes {@link #print(boolean)} and then
* {@link #println()}.
*
* @param x the boolean value to be printed
*/
public void println(boolean x) {
synchronized (lock) {
print(x);
println();
}
}
/**
* Prints a character and then terminates the line. This method behaves as
* though it invokes {@link #print(char)} and then {@link
* #println()}.
*
* @param x the char value to be printed
*/
public void println(char x) {
synchronized (lock) {
print(x);
println();
}
}
/**
* Prints an integer and then terminates the line. This method behaves as
* though it invokes {@link #print(int)} and then {@link
* #println()}.
*
* @param x the int value to be printed
*/
public void println(int x) {
synchronized (lock) {
print(x);
println();
}
}
/**
* Prints a long integer and then terminates the line. This method behaves
* as though it invokes {@link #print(long)} and then
* {@link #println()}.
*
* @param x the long value to be printed
*/
public void println(long x) {
synchronized (lock) {
print(x);
println();
}
}
/**
* Prints a floating-point number and then terminates the line. This method
* behaves as though it invokes {@link #print(float)} and then
* {@link #println()}.
*
* @param x the float value to be printed
*/
public void println(float x) {
synchronized (lock) {
print(x);
println();
}
}
/**
* Prints a double-precision floating-point number and then terminates the
* line. This method behaves as though it invokes {@link
* #print(double)} and then {@link #println()}.
*
* @param x the double value to be printed
*/
public void println(double x) {
synchronized (lock) {
print(x);
println();
}
}
/**
* Prints an array of characters and then terminates the line. This method
* behaves as though it invokes {@link #print(char[])} and then
* {@link #println()}.
*
* @param x the array of char values to be printed
*/
public void println(char x[]) {
synchronized (lock) {
print(x);
println();
}
}
/**
* Prints a String and then terminates the line. This method behaves as
* though it invokes {@link #print(String)} and then
* {@link #println()}.
*
* @param x the String value to be printed
*/
public void println(String x) {
synchronized (lock) {
print(x);
println();
}
}
/**
* Prints an Object and then terminates the line. This method calls
* at first String.valueOf(x) to get the printed object's string value,
* then behaves as
* though it invokes {@link #print(String)} and then
* {@link #println()}.
*
* @param x The Object to be printed.
*/
public void println(Object x) {
String s = String.valueOf(x);
synchronized (lock) {
print(s);
println();
}
}
/**
* A convenience method to write a formatted string to this writer using
* the specified format string and arguments. If automatic flushing is
* enabled, calls to this method will flush the output buffer.
*
*
An invocation of this method of the form out.printf(format, * args) behaves in exactly the same way as the invocation * *
* out.format(format, args)
*
* @param format
* A format string as described in Format string syntax.
*
* @param args
* Arguments referenced by the format specifiers in the format
* string. If there are more arguments than format specifiers, the
* extra arguments are ignored. The number of arguments is
* variable and may be zero. The maximum number of arguments is
* limited by the maximum dimension of a Java array as defined by
* The Java™ Virtual Machine Specification.
* The behaviour on a
* null argument depends on the conversion.
*
* @throws java.util.IllegalFormatException
* If a format string contains an illegal syntax, a format
* specifier that is incompatible with the given arguments,
* insufficient arguments given the format string, or other
* illegal conditions. For specification of all possible
* formatting errors, see the Details section of the
* formatter class specification.
*
* @throws NullPointerException
* If the format is null
*
* @return This writer
*
* @since 1.5
*/
public PrintWriter printf(String format, Object ... args) {
return format(format, args);
}
/**
* A convenience method to write a formatted string to this writer using
* the specified format string and arguments. If automatic flushing is
* enabled, calls to this method will flush the output buffer.
*
* An invocation of this method of the form out.printf(l, format, * args) behaves in exactly the same way as the invocation * *
* out.format(l, format, args)
*
* @param l
* The {@linkplain java.util.Locale locale} to apply during
* formatting. If l is null then no localization
* is applied.
*
* @param format
* A format string as described in Format string syntax.
*
* @param args
* Arguments referenced by the format specifiers in the format
* string. If there are more arguments than format specifiers, the
* extra arguments are ignored. The number of arguments is
* variable and may be zero. The maximum number of arguments is
* limited by the maximum dimension of a Java array as defined by
* The Java™ Virtual Machine Specification.
* The behaviour on a
* null argument depends on the conversion.
*
* @throws java.util.IllegalFormatException
* If a format string contains an illegal syntax, a format
* specifier that is incompatible with the given arguments,
* insufficient arguments given the format string, or other
* illegal conditions. For specification of all possible
* formatting errors, see the Details section of the
* formatter class specification.
*
* @throws NullPointerException
* If the format is null
*
* @return This writer
*
* @since 1.5
*/
public PrintWriter printf(Locale l, String format, Object ... args) {
return format(l, format, args);
}
/**
* Writes a formatted string to this writer using the specified format
* string and arguments. If automatic flushing is enabled, calls to this
* method will flush the output buffer.
*
* The locale always used is the one returned by {@link * java.util.Locale#getDefault() Locale.getDefault()}, regardless of any * previous invocations of other formatting methods on this object. * * @param format * A format string as described in Format string syntax. * * @param args * Arguments referenced by the format specifiers in the format * string. If there are more arguments than format specifiers, the * extra arguments are ignored. The number of arguments is * variable and may be zero. The maximum number of arguments is * limited by the maximum dimension of a Java array as defined by * The Java™ Virtual Machine Specification. * The behaviour on a * null argument depends on the conversion. * * @throws java.util.IllegalFormatException * If a format string contains an illegal syntax, a format * specifier that is incompatible with the given arguments, * insufficient arguments given the format string, or other * illegal conditions. For specification of all possible * formatting errors, see the Details section of the * Formatter class specification. * * @throws NullPointerException * If the format is null * * @return This writer * * @since 1.5 */ public PrintWriter format(String format, Object ... args) { try { synchronized (lock) { ensureOpen(); if ((formatter == null) || (formatter.locale() != Locale.getDefault())) formatter = new Formatter(this); formatter.format(Locale.getDefault(), format, args); if (autoFlush) out.flush(); } } catch (InterruptedIOException x) { Thread.currentThread().interrupt(); } catch (IOException x) { trouble = true; } return this; } /** * Writes a formatted string to this writer using the specified format * string and arguments. If automatic flushing is enabled, calls to this * method will flush the output buffer. * * @param l * The {@linkplain java.util.Locale locale} to apply during * formatting. If l is null then no localization * is applied. * * @param format * A format string as described in Format string syntax. * * @param args * Arguments referenced by the format specifiers in the format * string. If there are more arguments than format specifiers, the * extra arguments are ignored. The number of arguments is * variable and may be zero. The maximum number of arguments is * limited by the maximum dimension of a Java array as defined by * The Java™ Virtual Machine Specification. * The behaviour on a * null argument depends on the conversion. * * @throws java.util.IllegalFormatException * If a format string contains an illegal syntax, a format * specifier that is incompatible with the given arguments, * insufficient arguments given the format string, or other * illegal conditions. For specification of all possible * formatting errors, see the Details section of the * formatter class specification. * * @throws NullPointerException * If the format is null * * @return This writer * * @since 1.5 */ public PrintWriter format(Locale l, String format, Object ... args) { try { synchronized (lock) { ensureOpen(); if ((formatter == null) || (formatter.locale() != l)) formatter = new Formatter(this, l); formatter.format(l, format, args); if (autoFlush) out.flush(); } } catch (InterruptedIOException x) { Thread.currentThread().interrupt(); } catch (IOException x) { trouble = true; } return this; } /** * Appends the specified character sequence to this writer. * *
An invocation of this method of the form out.append(csq) * behaves in exactly the same way as the invocation * *
* out.write(csq.toString())
*
* Depending on the specification of toString for the * character sequence csq, the entire sequence may not be * appended. For instance, invoking the toString method of a * character buffer will return a subsequence whose content depends upon * the buffer's position and limit. * * @param csq * The character sequence to append. If csq is * null, then the four characters "null" are * appended to this writer. * * @return This writer * * @since 1.5 */ public PrintWriter append(CharSequence csq) { if (csq == null) write("null"); else write(csq.toString()); return this; } /** * Appends a subsequence of the specified character sequence to this writer. * *
An invocation of this method of the form out.append(csq, start, * end) when csq is not null, behaves in * exactly the same way as the invocation * *
* out.write(csq.subSequence(start, end).toString())
*
* @param csq
* The character sequence from which a subsequence will be
* appended. If csq is null, then characters
* will be appended as if csq contained the four
* characters "null".
*
* @param start
* The index of the first character in the subsequence
*
* @param end
* The index of the character following the last character in the
* subsequence
*
* @return This writer
*
* @throws IndexOutOfBoundsException
* If start or end are negative, start
* is greater than end, or end is greater than
* csq.length()
*
* @since 1.5
*/
public PrintWriter append(CharSequence csq, int start, int end) {
CharSequence cs = (csq == null ? "null" : csq);
write(cs.subSequence(start, end).toString());
return this;
}
/**
* Appends the specified character to this writer.
*
* An invocation of this method of the form out.append(c) * behaves in exactly the same way as the invocation * *
* out.write(c)
*
* @param c
* The 16-bit character to append
*
* @return This writer
*
* @since 1.5
*/
public PrintWriter append(char c) {
write(c);
return this;
}
}