1 /*
2 * Copyright (c) 1994, 2006, 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 JDK1.0
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 JDK1.1
62 */
63 public static final Class<Boolean> TYPE = Class.getPrimitiveClass("boolean");
64
65 /**
66 * The value of the Boolean.
67 *
68 * @serial
69 */
70 private final boolean value;
71
72 /** use serialVersionUID from JDK 1.0.2 for interoperability */
73 private static final long serialVersionUID = -3665804199014368530L;
74
75 /**
76 * Allocates a {@code Boolean} object representing the
77 * {@code value} argument.
78 *
79 * <p><b>Note: It is rarely appropriate to use this constructor.
80 * Unless a <i>new</i> instance is required, the static factory
81 * {@link #valueOf(boolean)} is generally a better choice. It is
82 * likely to yield significantly better space and time performance.</b>
83 *
84 * @param value the value of the {@code Boolean}.
85 */
86 public Boolean(boolean value) {
87 this.value = value;
88 }
89
90 /**
91 * Allocates a {@code Boolean} object representing the value
92 * {@code true} if the string argument is not {@code null}
93 * and is equal, ignoring case, to the string {@code "true"}.
94 * Otherwise, allocate a {@code Boolean} object representing the
95 * value {@code false}. Examples:<p>
96 * {@code new Boolean("True")} produces a {@code Boolean} object
97 * that represents {@code true}.<br>
98 * {@code new Boolean("yes")} produces a {@code Boolean} object
99 * that represents {@code false}.
100 *
101 * @param s the string to be converted to a {@code Boolean}.
102 */
103 public Boolean(String s) {
104 this(toBoolean(s));
105 }
106
107 /**
108 * Parses the string argument as a boolean. The {@code boolean}
109 * returned represents the value {@code true} if the string argument
110 * is not {@code null} and is equal, ignoring case, to the string
111 * {@code "true"}. <p>
112 * Example: {@code Boolean.parseBoolean("True")} returns {@code true}.<br>
113 * Example: {@code Boolean.parseBoolean("yes")} returns {@code false}.
114 *
115 * @param s the {@code String} containing the boolean
116 * representation to be parsed
117 * @return the boolean represented by the string argument
118 * @since 1.5
119 */
120 public static boolean parseBoolean(String s) {
121 return toBoolean(s);
122 }
123
124 /**
125 * Returns the value of this {@code Boolean} object as a boolean
126 * primitive.
127 *
128 * @return the primitive {@code boolean} value of this object.
129 */
130 public boolean booleanValue() {
131 return value;
132 }
133
134 /**
135 * Returns a {@code Boolean} instance representing the specified
136 * {@code boolean} value. If the specified {@code boolean} value
137 * is {@code true}, this method returns {@code Boolean.TRUE};
138 * if it is {@code false}, this method returns {@code Boolean.FALSE}.
139 * If a new {@code Boolean} instance is not required, this method
140 * should generally be used in preference to the constructor
141 * {@link #Boolean(boolean)}, as this method is likely to yield
142 * significantly better space and time performance.
143 *
144 * @param b a boolean value.
145 * @return a {@code Boolean} instance representing {@code b}.
146 * @since 1.4
147 */
148 public static Boolean valueOf(boolean b) {
149 return (b ? TRUE : FALSE);
150 }
151
152 /**
153 * Returns a {@code Boolean} with a value represented by the
154 * specified string. The {@code Boolean} returned represents a
155 * true value if the string argument is not {@code null}
156 * and is equal, ignoring case, to the string {@code "true"}.
157 *
158 * @param s a string.
159 * @return the {@code Boolean} value represented by the string.
160 */
161 public static Boolean valueOf(String s) {
162 return toBoolean(s) ? TRUE : FALSE;
163 }
164
165 /**
166 * Returns a {@code String} object representing the specified
167 * boolean. If the specified boolean is {@code true}, then
168 * the string {@code "true"} will be returned, otherwise the
169 * string {@code "false"} will be returned.
170 *
171 * @param b the boolean to be converted
172 * @return the string representation of the specified {@code boolean}
173 * @since 1.4
174 */
175 public static String toString(boolean b) {
176 return b ? "true" : "false";
177 }
178
179 /**
180 * Returns a {@code String} object representing this Boolean's
181 * value. If this object represents the value {@code true},
182 * a string equal to {@code "true"} is returned. Otherwise, a
183 * string equal to {@code "false"} is returned.
184 *
185 * @return a string representation of this object.
186 */
187 public String toString() {
188 return value ? "true" : "false";
189 }
190
191 /**
192 * Returns a hash code for this {@code Boolean} object.
193 *
194 * @return the integer {@code 1231} if this object represents
195 * {@code true}; returns the integer {@code 1237} if this
196 * object represents {@code false}.
197 */
198 public int hashCode() {
199 return value ? 1231 : 1237;
200 }
201
202 /**
203 * Returns {@code true} if and only if the argument is not
204 * {@code null} and is a {@code Boolean} object that
205 * represents the same {@code boolean} value as this object.
206 *
207 * @param obj the object to compare with.
208 * @return {@code true} if the Boolean objects represent the
209 * same value; {@code false} otherwise.
210 */
211 public boolean equals(Object obj) {
212 if (obj instanceof Boolean) {
213 return value == ((Boolean)obj).booleanValue();
214 }
215 return false;
216 }
217
218 /**
219 * Returns {@code true} if and only if the system property
220 * named by the argument exists and is equal to the string
221 * {@code "true"}. (Beginning with version 1.0.2 of the
222 * Java<small><sup>TM</sup></small> platform, the test of
223 * this string is case insensitive.) A system property is accessible
224 * through {@code getProperty}, a method defined by the
225 * {@code System} class.
226 * <p>
227 * If there is no property with the specified name, or if the specified
228 * name is empty or null, then {@code false} is returned.
229 *
230 * @param name the system property name.
231 * @return the {@code boolean} value of the system property.
232 * @see java.lang.System#getProperty(java.lang.String)
233 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
234 */
235 public static boolean getBoolean(String name) {
236 boolean result = false;
237 try {
238 result = toBoolean(System.getProperty(name));
239 } catch (IllegalArgumentException e) {
240 } catch (NullPointerException e) {
241 }
242 return result;
243 }
244
245 /**
246 * Compares this {@code Boolean} instance with another.
247 *
248 * @param b the {@code Boolean} instance to be compared
249 * @return zero if this object represents the same boolean value as the
250 * argument; a positive value if this object represents true
251 * and the argument represents false; and a negative value if
252 * this object represents false and the argument represents true
253 * @throws NullPointerException if the argument is {@code null}
254 * @see Comparable
255 * @since 1.5
256 */
257 public int compareTo(Boolean b) {
258 return compare(this.value, b.value);
259 }
260
261 /**
262 * Compares two {@code boolean} values.
263 * The value returned is identical to what would be returned by:
264 * <pre>
265 * Boolean.valueOf(x).compareTo(Boolean.valueOf(y))
266 * </pre>
267 *
268 * @param x the first {@code boolean} to compare
269 * @param y the second {@code boolean} to compare
270 * @return the value {@code 0} if {@code x == y};
271 * a value less than {@code 0} if {@code !x && y}; and
272 * a value greater than {@code 0} if {@code x && !y}
273 * @since 1.7
274 */
275 public static int compare(boolean x, boolean y) {
276 return (x == y) ? 0 : (x ? 1 : -1);
277 }
278
279 private static boolean toBoolean(String name) {
280 return ((name != null) && name.equalsIgnoreCase("true"));
281 }
282 }