001: /*
002: * Copyright 1994-2006 Sun Microsystems, Inc. All Rights Reserved.
003: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004: *
005: * This code is free software; you can redistribute it and/or modify it
006: * under the terms of the GNU General Public License version 2 only, as
007: * published by the Free Software Foundation. Sun designates this
008: * particular file as subject to the "Classpath" exception as provided
009: * by Sun in the LICENSE file that accompanied this code.
010: *
011: * This code is distributed in the hope that it will be useful, but WITHOUT
012: * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013: * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014: * version 2 for more details (a copy is included in the LICENSE file that
015: * accompanied this code).
016: *
017: * You should have received a copy of the GNU General Public License version
018: * 2 along with this work; if not, write to the Free Software Foundation,
019: * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020: *
021: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022: * CA 95054 USA or visit www.sun.com if you need additional information or
023: * have any questions.
024: */
025:
026: package java.lang;
027:
028: /**
029: * The Boolean class wraps a value of the primitive type
030: * {@code boolean} in an object. An object of type
031: * {@code Boolean} contains a single field whose type is
032: * {@code boolean}.
033: * <p>
034: * In addition, this class provides many methods for
035: * converting a {@code boolean} to a {@code String} and a
036: * {@code String} to a {@code boolean}, as well as other
037: * constants and methods useful when dealing with a
038: * {@code boolean}.
039: *
040: * @author Arthur van Hoff
041: * @version 1.60, 05/05/07
042: * @since JDK1.0
043: */
044: public final class Boolean implements java.io.Serializable,
045: Comparable<Boolean> {
046: /**
047: * The {@code Boolean} object corresponding to the primitive
048: * value {@code true}.
049: */
050: public static final Boolean TRUE = new Boolean(true);
051:
052: /**
053: * The {@code Boolean} object corresponding to the primitive
054: * value {@code false}.
055: */
056: public static final Boolean FALSE = new Boolean(false);
057:
058: /**
059: * The Class object representing the primitive type boolean.
060: *
061: * @since JDK1.1
062: */
063: public static final Class<Boolean> TYPE = Class
064: .getPrimitiveClass("boolean");
065:
066: /**
067: * The value of the Boolean.
068: *
069: * @serial
070: */
071: private final boolean value;
072:
073: /** use serialVersionUID from JDK 1.0.2 for interoperability */
074: private static final long serialVersionUID = -3665804199014368530L;
075:
076: /**
077: * Allocates a {@code Boolean} object representing the
078: * {@code value} argument.
079: *
080: * <p><b>Note: It is rarely appropriate to use this constructor.
081: * Unless a <i>new</i> instance is required, the static factory
082: * {@link #valueOf(boolean)} is generally a better choice. It is
083: * likely to yield significantly better space and time performance.</b>
084: *
085: * @param value the value of the {@code Boolean}.
086: */
087: public Boolean(boolean value) {
088: this .value = value;
089: }
090:
091: /**
092: * Allocates a {@code Boolean} object representing the value
093: * {@code true} if the string argument is not {@code null}
094: * and is equal, ignoring case, to the string {@code "true"}.
095: * Otherwise, allocate a {@code Boolean} object representing the
096: * value {@code false}. Examples:<p>
097: * {@code new Boolean("True")} produces a {@code Boolean} object
098: * that represents {@code true}.<br>
099: * {@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 (toBoolean(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 toBoolean(s);
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 toBoolean(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: public int hashCode() {
200: return value ? 1231 : 1237;
201: }
202:
203: /**
204: * Returns {@code true} if and only if the argument is not
205: * {@code null} and is a {@code Boolean} object that
206: * represents the same {@code boolean} value as this object.
207: *
208: * @param obj the object to compare with.
209: * @return {@code true} if the Boolean objects represent the
210: * same value; {@code false} otherwise.
211: */
212: public boolean equals(Object obj) {
213: if (obj instanceof Boolean) {
214: return value == ((Boolean) obj).booleanValue();
215: }
216: return false;
217: }
218:
219: /**
220: * Returns {@code true} if and only if the system property
221: * named by the argument exists and is equal to the string
222: * {@code "true"}. (Beginning with version 1.0.2 of the
223: * Java<small><sup>TM</sup></small> platform, the test of
224: * this string is case insensitive.) A system property is accessible
225: * through {@code getProperty}, a method defined by the
226: * {@code System} class.
227: * <p>
228: * If there is no property with the specified name, or if the specified
229: * name is empty or null, then {@code false} is returned.
230: *
231: * @param name the system property name.
232: * @return the {@code boolean} value of the system property.
233: * @see java.lang.System#getProperty(java.lang.String)
234: * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
235: */
236: public static boolean getBoolean(String name) {
237: boolean result = false;
238: try {
239: result = toBoolean(System.getProperty(name));
240: } catch (IllegalArgumentException e) {
241: } catch (NullPointerException e) {
242: }
243: return result;
244: }
245:
246: /**
247: * Compares this {@code Boolean} instance with another.
248: *
249: * @param b the {@code Boolean} instance to be compared
250: * @return zero if this object represents the same boolean value as the
251: * argument; a positive value if this object represents true
252: * and the argument represents false; and a negative value if
253: * this object represents false and the argument represents true
254: * @throws NullPointerException if the argument is {@code null}
255: * @see Comparable
256: * @since 1.5
257: */
258: public int compareTo(Boolean b) {
259: return (b.value == value ? 0 : (value ? 1 : -1));
260: }
261:
262: private static boolean toBoolean(String name) {
263: return ((name != null) && name.equalsIgnoreCase("true"));
264: }
265: }
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