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 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 @SuppressWarnings("unchecked") 64 public static final Class<Boolean> TYPE = (Class<Boolean>) boolean[].class.getComponentType(); 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 234 * named by the argument exists and is equal to the string 235 * {@code "true"}. (Beginning with version 1.0.2 of the 236 * Java<small><sup>TM</sup></small> platform, the test of 237 * this string is case insensitive.) A system property is accessible 238 * through {@code getProperty}, a method defined by the 239 * {@code System} class. 240 * <p> 241 * If there is no property with the specified name, or if the specified 242 * name is empty or null, then {@code false} is returned. 243 * 244 * @param name the system property name. 245 * @return the {@code boolean} value of the system property. 246 * @throws SecurityException for the same reasons as 247 * {@link System#getProperty(String) System.getProperty} 248 * @see java.lang.System#getProperty(java.lang.String) 249 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 250 */ 251 public static boolean getBoolean(String name) { 252 boolean result = false; 253 try { 254 result = parseBoolean(System.getProperty(name)); 255 } catch (IllegalArgumentException | NullPointerException e) { 256 } 257 return result; 258 } 259 260 /** 261 * Compares this {@code Boolean} instance with another. 262 * 263 * @param b the {@code Boolean} instance to be compared 264 * @return zero if this object represents the same boolean value as the 265 * argument; a positive value if this object represents true 266 * and the argument represents false; and a negative value if 267 * this object represents false and the argument represents true 268 * @throws NullPointerException if the argument is {@code null} 269 * @see Comparable 270 * @since 1.5 271 */ 272 public int compareTo(Boolean b) { 273 return compare(this.value, b.value); 274 } 275 276 /** 277 * Compares two {@code boolean} values. 278 * The value returned is identical to what would be returned by: 279 * <pre> 280 * Boolean.valueOf(x).compareTo(Boolean.valueOf(y)) 281 * </pre> 282 * 283 * @param x the first {@code boolean} to compare 284 * @param y the second {@code boolean} to compare 285 * @return the value {@code 0} if {@code x == y}; 286 * a value less than {@code 0} if {@code !x && y}; and 287 * a value greater than {@code 0} if {@code x && !y} 288 * @since 1.7 289 */ 290 public static int compare(boolean x, boolean y) { 291 return (x == y) ? 0 : (x ? 1 : -1); 292 } 293 294 /** 295 * Returns the result of applying the logical AND operator to the 296 * specified {@code boolean} operands. 297 * 298 * @param a the first operand 299 * @param b the second operand 300 * @return the logical AND of {@code a} and {@code b} 301 * @see java.util.function.BinaryOperator 302 * @since 1.8 303 */ 304 public static boolean logicalAnd(boolean a, boolean b) { 305 return a && b; 306 } 307 308 /** 309 * Returns the result of applying the logical OR operator to the 310 * specified {@code boolean} operands. 311 * 312 * @param a the first operand 313 * @param b the second operand 314 * @return the logical OR of {@code a} and {@code b} 315 * @see java.util.function.BinaryOperator 316 * @since 1.8 317 */ 318 public static boolean logicalOr(boolean a, boolean b) { 319 return a || b; 320 } 321 322 /** 323 * Returns the result of applying the logical XOR operator to the 324 * specified {@code boolean} operands. 325 * 326 * @param a the first operand 327 * @param b the second operand 328 * @return the logical XOR of {@code a} and {@code b} 329 * @see java.util.function.BinaryOperator 330 * @since 1.8 331 */ 332 public static boolean logicalXor(boolean a, boolean b) { 333 return a ^ b; 334 } 335 } 336
