1 /*
2 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang;
27
28 /**
29 * The Boolean class wraps a value of the primitive type
30 * {@code boolean} in an object. An object of type
31 * {@code Boolean} contains a single field whose type is
32 * {@code boolean}.
33 * <p>
34 * In addition, this class provides many methods for
35 * converting a {@code boolean} to a {@code String} and a
36 * {@code String} to a {@code boolean}, as well as other
37 * constants and methods useful when dealing with a
38 * {@code boolean}.
39 *
40 * @author Arthur van Hoff
41 * @since 1.0
42 */
43 public final class Boolean implements java.io.Serializable,
44 Comparable<Boolean>
45 {
46 /**
47 * The {@code Boolean} object corresponding to the primitive
48 * value {@code true}.
49 */
50 public static final Boolean TRUE = new Boolean(true);
51
52 /**
53 * The {@code Boolean} object corresponding to the primitive
54 * value {@code false}.
55 */
56 public static final Boolean FALSE = new Boolean(false);
57
58 /**
59 * The Class object representing the primitive type boolean.
60 *
61 * @since 1.1
62 */
63 @SuppressWarnings("unchecked")
64 public static final Class<Boolean> TYPE = (Class<Boolean>) Class.getPrimitiveClass("boolean");
65
66 /**
67 * The value of the Boolean.
68 *
69 * @serial
70 */
71 private final boolean value;
72
73 /** use serialVersionUID from JDK 1.0.2 for interoperability */
74 private static final long serialVersionUID = -3665804199014368530L;
75
76 /**
77 * Allocates a {@code Boolean} object representing the
78 * {@code value} argument.
79 *
80 * <p><b>Note: It is rarely appropriate to use this constructor.
81 * Unless a <i>new</i> instance is required, the static factory
82 * {@link #valueOf(boolean)} is generally a better choice. It is
83 * likely to yield significantly better space and time performance.</b>
84 *
85 * @param value the value of the {@code Boolean}.
86 */
87 public Boolean(boolean value) {
88 this.value = value;
89 }
90
91 /**
92 * Allocates a {@code Boolean} object representing the value
93 * {@code true} if the string argument is not {@code null}
94 * and is equal, ignoring case, to the string {@code "true"}.
95 * Otherwise, allocate a {@code Boolean} object representing the
96 * value {@code false}. Examples:<p>
97 * {@code new Boolean("True")} produces a {@code Boolean} object
98 * that represents {@code true}.<br>
99 * {@code new Boolean("yes")} produces a {@code Boolean} object
100 * that represents {@code false}.
101 *
102 * @param s the string to be converted to a {@code Boolean}.
103 */
104 public Boolean(String s) {
105 this(parseBoolean(s));
106 }
107
108 /**
109 * Parses the string argument as a boolean. The {@code boolean}
110 * returned represents the value {@code true} if the string argument
111 * is not {@code null} and is equal, ignoring case, to the string
112 * {@code "true"}. <p>
113 * Example: {@code Boolean.parseBoolean("True")} returns {@code true}.<br>
114 * Example: {@code Boolean.parseBoolean("yes")} returns {@code false}.
115 *
116 * @param s the {@code String} containing the boolean
117 * representation to be parsed
118 * @return the boolean represented by the string argument
119 * @since 1.5
120 */
121 public static boolean parseBoolean(String s) {
122 return ((s != null) && s.equalsIgnoreCase("true"));
123 }
124
125 /**
126 * Returns the value of this {@code Boolean} object as a boolean
127 * primitive.
128 *
129 * @return the primitive {@code boolean} value of this object.
130 */
131 public boolean booleanValue() {
132 return value;
133 }
134
135 /**
136 * Returns a {@code Boolean} instance representing the specified
137 * {@code boolean} value. If the specified {@code boolean} value
138 * is {@code true}, this method returns {@code Boolean.TRUE};
139 * if it is {@code false}, this method returns {@code Boolean.FALSE}.
140 * If a new {@code Boolean} instance is not required, this method
141 * should generally be used in preference to the constructor
142 * {@link #Boolean(boolean)}, as this method is likely to yield
143 * significantly better space and time performance.
144 *
145 * @param b a boolean value.
146 * @return a {@code Boolean} instance representing {@code b}.
147 * @since 1.4
148 */
149 public static Boolean valueOf(boolean b) {
150 return (b ? TRUE : FALSE);
151 }
152
153 /**
154 * Returns a {@code Boolean} with a value represented by the
155 * specified string. The {@code Boolean} returned represents a
156 * true value if the string argument is not {@code null}
157 * and is equal, ignoring case, to the string {@code "true"}.
158 *
159 * @param s a string.
160 * @return the {@code Boolean} value represented by the string.
161 */
162 public static Boolean valueOf(String s) {
163 return parseBoolean(s) ? TRUE : FALSE;
164 }
165
166 /**
167 * Returns a {@code String} object representing the specified
168 * boolean. If the specified boolean is {@code true}, then
169 * the string {@code "true"} will be returned, otherwise the
170 * string {@code "false"} will be returned.
171 *
172 * @param b the boolean to be converted
173 * @return the string representation of the specified {@code boolean}
174 * @since 1.4
175 */
176 public static String toString(boolean b) {
177 return b ? "true" : "false";
178 }
179
180 /**
181 * Returns a {@code String} object representing this Boolean's
182 * value. If this object represents the value {@code true},
183 * a string equal to {@code "true"} is returned. Otherwise, a
184 * string equal to {@code "false"} is returned.
185 *
186 * @return a string representation of this object.
187 */
188 public String toString() {
189 return value ? "true" : "false";
190 }
191
192 /**
193 * Returns a hash code for this {@code Boolean} object.
194 *
195 * @return the integer {@code 1231} if this object represents
196 * {@code true}; returns the integer {@code 1237} if this
197 * object represents {@code false}.
198 */
199 @Override
200 public int hashCode() {
201 return Boolean.hashCode(value);
202 }
203
204 /**
205 * Returns a hash code for a {@code boolean} value; compatible with
206 * {@code Boolean.hashCode()}.
207 *
208 * @param value the value to hash
209 * @return a hash code value for a {@code boolean} value.
210 * @since 1.8
211 */
212 public static int hashCode(boolean value) {
213 return value ? 1231 : 1237;
214 }
215
216 /**
217 * Returns {@code true} if and only if the argument is not
218 * {@code null} and is a {@code Boolean} object that
219 * represents the same {@code boolean} value as this object.
220 *
221 * @param obj the object to compare with.
222 * @return {@code true} if the Boolean objects represent the
223 * same value; {@code false} otherwise.
224 */
225 public boolean equals(Object obj) {
226 if (obj instanceof Boolean) {
227 return value == ((Boolean)obj).booleanValue();
228 }
229 return false;
230 }
231
232 /**
233 * Returns {@code true} if and only if the system property named
234 * by the argument exists and is equal to the string {@code
235 * "true"}. (Beginning with version 1.0.2 of the Java™
236 * platform, the test of this string is case insensitive.) A
237 * system property is accessible through {@code getProperty}, a
238 * method defined by the {@code System} class.
239 * <p>
240 * If there is no property with the specified name, or if the specified
241 * name is empty or null, then {@code false} is returned.
242 *
243 * @param name the system property name.
244 * @return the {@code boolean} value of the system property.
245 * @throws SecurityException for the same reasons as
246 * {@link System#getProperty(String) System.getProperty}
247 * @see java.lang.System#getProperty(java.lang.String)
248 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
249 */
250 public static boolean getBoolean(String name) {
251 boolean result = false;
252 try {
253 result = parseBoolean(System.getProperty(name));
254 } catch (IllegalArgumentException | NullPointerException e) {
255 }
256 return result;
257 }
258
259 /**
260 * Compares this {@code Boolean} instance with another.
261 *
262 * @param b the {@code Boolean} instance to be compared
263 * @return zero if this object represents the same boolean value as the
264 * argument; a positive value if this object represents true
265 * and the argument represents false; and a negative value if
266 * this object represents false and the argument represents true
267 * @throws NullPointerException if the argument is {@code null}
268 * @see Comparable
269 * @since 1.5
270 */
271 public int compareTo(Boolean b) {
272 return compare(this.value, b.value);
273 }
274
275 /**
276 * Compares two {@code boolean} values.
277 * The value returned is identical to what would be returned by:
278 * <pre>
279 * Boolean.valueOf(x).compareTo(Boolean.valueOf(y))
280 * </pre>
281 *
282 * @param x the first {@code boolean} to compare
283 * @param y the second {@code boolean} to compare
284 * @return the value {@code 0} if {@code x == y};
285 * a value less than {@code 0} if {@code !x && y}; and
286 * a value greater than {@code 0} if {@code x && !y}
287 * @since 1.7
288 */
289 public static int compare(boolean x, boolean y) {
290 return (x == y) ? 0 : (x ? 1 : -1);
291 }
292
293 /**
294 * Returns the result of applying the logical AND operator to the
295 * specified {@code boolean} operands.
296 *
297 * @param a the first operand
298 * @param b the second operand
299 * @return the logical AND of {@code a} and {@code b}
300 * @see java.util.function.BinaryOperator
301 * @since 1.8
302 */
303 public static boolean logicalAnd(boolean a, boolean b) {
304 return a && b;
305 }
306
307 /**
308 * Returns the result of applying the logical OR operator to the
309 * specified {@code boolean} operands.
310 *
311 * @param a the first operand
312 * @param b the second operand
313 * @return the logical OR of {@code a} and {@code b}
314 * @see java.util.function.BinaryOperator
315 * @since 1.8
316 */
317 public static boolean logicalOr(boolean a, boolean b) {
318 return a || b;
319 }
320
321 /**
322 * Returns the result of applying the logical XOR operator to the
323 * specified {@code boolean} operands.
324 *
325 * @param a the first operand
326 * @param b the second operand
327 * @return the logical XOR of {@code a} and {@code b}
328 * @see java.util.function.BinaryOperator
329 * @since 1.8
330 */
331 public static boolean logicalXor(boolean a, boolean b) {
332 return a ^ b;
333 }
334 }