1 /* 2 * Copyright (c) 1994, 2011, 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(parseBoolean(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 ((s != null) && s.equalsIgnoreCase("true")); 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 parseBoolean(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 * @throws SecurityException for the same reasons as 233 * {@link System#getProperty(String) System.getProperty} 234 * @see java.lang.System#getProperty(java.lang.String) 235 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 236 */ 237 public static boolean getBoolean(String name) { 238 boolean result = false; 239 try { 240 result = parseBoolean(System.getProperty(name)); 241 } catch (IllegalArgumentException | 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 compare(this.value, b.value); 260 } 261 262 /** 263 * Compares two {@code boolean} values. 264 * The value returned is identical to what would be returned by: 265 * <pre> 266 * Boolean.valueOf(x).compareTo(Boolean.valueOf(y)) 267 * </pre> 268 * 269 * @param x the first {@code boolean} to compare 270 * @param y the second {@code boolean} to compare 271 * @return the value {@code 0} if {@code x == y}; 272 * a value less than {@code 0} if {@code !x && y}; and 273 * a value greater than {@code 0} if {@code x && !y} 274 * @since 1.7 275 */ 276 public static int compare(boolean x, boolean y) { 277 return (x == y) ? 0 : (x ? 1 : -1); 278 } 279 }