Source Code of Java - Boolean

港控/mmm° 2021-09-10 15:56 241阅读 0赞

/* * %W% %E% * * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved. * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */
 
 package java.lang;
 
 /** * The Boolean class wraps a value of the primitive type * <code>boolean</code> in an object. An object of type * <code>Boolean</code> contains a single field whose type is * <code>boolean</code>. * * In addition, this class provides many methods for * converting a <code>boolean</code> to a <code>String</code> and a * <code>String</code> to a <code>boolean</code>, as well as other * constants and methods useful when dealing with a * <code>boolean</code>. * * @author Arthur van Hoff * @version %I%, %G% * @since JDK1.0 */
 public final class Boolean implements java.io.Serializable, Comparable<Boolean> { 
 /** * The <code>Boolean</code> object corresponding to the primitive * value <code>true</code>. */
 public static final Boolean TRUE = new Boolean(true);
 
 /** * The <code>Boolean</code> object corresponding to the primitive * value <code>false</code>. */
 public static final Boolean FALSE = new Boolean(false);
 
 /** * The Class object representing the primitive type boolean. * * @since JDK1.1 */
 public static final Class<Boolean> TYPE = Class.getPrimitiveClass("boolean");
 
 /** * The value of the Boolean. * * @serial */
 private final boolean value;
 
 /** use serialVersionUID from JDK 1.0.2 for interoperability */
 private static final long serialVersionUID = -3665804199014368530L;
 
 /** * Allocates a <code>Boolean</code> object representing the * <code>value</code> argument. * * Note: It is rarely appropriate to use this constructor. * Unless a new instance is required, the static factory * {@link #valueOf(boolean)} is generally a better choice. It is * likely to yield significantly better space and time performance. * * @param value the value of the <code>Boolean</code>. */
 public Boolean(boolean value) {
 this.value = value;
 }
 
 /** * Allocates a <code>Boolean</code> object representing the value * <code>true</code> if the string argument is not <code>null</code> * and is equal, ignoring case, to the string {@code "true"}. * Otherwise, allocate a <code>Boolean</code> object representing the * value <code>false</code>. Examples: * {@code new Boolean("True")} produces a <tt>Boolean</tt> object * that represents <tt>true</tt>. * {@code new Boolean("yes")} produces a <tt>Boolean</tt> object * that represents <tt>false</tt>. * * @param s the string to be converted to a <code>Boolean</code>. */
 public Boolean(String s) {
 this(toBoolean(s));
 }
 
 /** * Parses the string argument as a boolean. The <code>boolean</code> * returned represents the value <code>true</code> if the string argument * is not <code>null</code> and is equal, ignoring case, to the string * {@code "true"}. * Example: {@code Boolean.parseBoolean("True")} returns <tt>true</tt>. * Example: {@code Boolean.parseBoolean("yes")} returns <tt>false</tt>. * * @param s the <code>String</code> containing the boolean * representation to be parsed * @return the boolean represented by the string argument * @since 1.5 */
 public static boolean parseBoolean(String s) {
 return toBoolean(s);
 }
 
 /** * Returns the value of this <tt>Boolean</tt> object as a boolean * primitive. * * @return the primitive <code>boolean</code> value of this object. */
 public boolean booleanValue() {
 return value;
 }
 
 /** * Returns a <tt>Boolean</tt> instance representing the specified * <tt>boolean</tt> value. If the specified <tt>boolean</tt> value * is <tt>true</tt>, this method returns <tt>Boolean.TRUE</tt>; * if it is <tt>false</tt>, this method returns <tt>Boolean.FALSE</tt>. * If a new <tt>Boolean</tt> instance is not required, this method * should generally be used in preference to the constructor * {@link #Boolean(boolean)}, as this method is likely to yield * significantly better space and time performance. * * @param b a boolean value. * @return a <tt>Boolean</tt> instance representing <tt>b</tt>. * @since 1.4 */
 public static Boolean valueOf(boolean b) {
 return (b ? TRUE : FALSE);
 }
 
 /** * Returns a <code>Boolean</code> with a value represented by the * specified string. The <code>Boolean</code> returned represents a * true value if the string argument is not <code>null</code> * and is equal, ignoring case, to the string {@code "true"}. * * @param s a string. * @return the <code>Boolean</code> value represented by the string. */
 public static Boolean valueOf(String s) {
 return toBoolean(s) ? TRUE : FALSE;
 }
 
 /** * Returns a <tt>String</tt> object representing the specified * boolean. If the specified boolean is <code>true</code>, then * the string {@code "true"} will be returned, otherwise the * string {@code "false"} will be returned. * * @param b the boolean to be converted * @return the string representation of the specified <code>boolean</code> * @since 1.4 */
 public static String toString(boolean b) {
 return b ? "true" : "false";
 }
 
 /** * Returns a <tt>String</tt> object representing this Boolean's * value. If this object represents the value <code>true</code>, * a string equal to {@code "true"} is returned. Otherwise, a * string equal to {@code "false"} is returned. * * @return a string representation of this object. */
 public String toString() {
 return value ? "true" : "false";
 }
 
 /** * Returns a hash code for this <tt>Boolean</tt> object. * * @return the integer <tt>1231</tt> if this object represents * <tt>true</tt>; returns the integer <tt>1237</tt> if this * object represents <tt>false</tt>. */
 public int hashCode() {
 return value ? 1231 : 1237;
 }
 
 /** * Returns <code>true</code> if and only if the argument is not * <code>null</code> and is a <code>Boolean</code> object that * represents the same <code>boolean</code> value as this object. * * @param obj the object to compare with. * @return <code>true</code> if the Boolean objects represent the * same value; <code>false</code> otherwise. */
 public boolean equals(Object obj) {
 if (obj instanceof Boolean) {
 return value == ((Boolean)obj).booleanValue();
 } 
 return false;
 }
 
 /** * Returns <code>true</code> if and only if the system property * named by the argument exists and is equal to the string * {@code "true"}. (Beginning with version 1.0.2 of the * JavaTM platform, the test of * this string is case insensitive.) A system property is accessible * through <code>getProperty</code>, a method defined by the * <code>System</code> class. * * If there is no property with the specified name, or if the specified * name is empty or null, then <code>false</code> is returned. * * @param name the system property name. * @return the <code>boolean</code> value of the system property. * @see java.lang.System#getProperty(java.lang.String) * @see java.lang.System#getProperty(java.lang.String, java.lang.String) */
 public static boolean getBoolean(String name) {
 boolean result = false;
 try {
 result = toBoolean(System.getProperty(name));
 } catch (IllegalArgumentException e) {
 } catch (NullPointerException e) {
 }
 return result;
 }
 
 /** * Compares this <tt>Boolean</tt> instance with another. * * @param b the <tt>Boolean</tt> instance to be compared * @return zero if this object represents the same boolean value as the * argument; a positive value if this object represents true * and the argument represents false; and a negative value if * this object represents false and the argument represents true * @throws NullPointerException if the argument is <tt>null</tt> * @see Comparable * @since 1.5 */
 public int compareTo(Boolean b) {
 return (b.value == value ? 0 : (value ? 1 : -1));
 }
 
 private static boolean toBoolean(String name) { 
 return ((name != null) && name.equalsIgnoreCase("true"));
 }
 }

来源：[http://blog.csdn.net/f562867448/article/details/8688155][http_blog.csdn.net_f562867448_article_details_8688155]

[http_blog.csdn.net_f562867448_article_details_8688155]: http://blog.csdn.net/f562867448/article/details/8688155