jdk/src/share/classes/java/lang/Boolean.java
author ohair
Tue, 25 May 2010 15:58:33 -0700
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6943119: Rebrand source copyright notices Reviewed-by: darcy, weijun
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/*
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 * Copyright (c) 1994, 2006, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.  Oracle designates this
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 * particular file as subject to the "Classpath" exception as provided
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 * by Oracle in the LICENSE file that accompanied this code.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 */
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package java.lang;
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/**
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 * The Boolean class wraps a value of the primitive type
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 * {@code boolean} in an object. An object of type
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 * {@code Boolean} contains a single field whose type is
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 * {@code boolean}.
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 * <p>
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 * In addition, this class provides many methods for
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 * converting a {@code boolean} to a {@code String} and a
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 * {@code String} to a {@code boolean}, as well as other
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 * constants and methods useful when dealing with a
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 * {@code boolean}.
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 *
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 * @author  Arthur van Hoff
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 * @since   JDK1.0
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 */
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public final class Boolean implements java.io.Serializable,
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                                      Comparable<Boolean>
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{
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    /**
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     * The {@code Boolean} object corresponding to the primitive
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     * value {@code true}.
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     */
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    public static final Boolean TRUE = new Boolean(true);
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    /**
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     * The {@code Boolean} object corresponding to the primitive
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     * value {@code false}.
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     */
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    public static final Boolean FALSE = new Boolean(false);
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    /**
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     * The Class object representing the primitive type boolean.
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     *
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     * @since   JDK1.1
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     */
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    public static final Class<Boolean> TYPE = Class.getPrimitiveClass("boolean");
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    /**
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     * The value of the Boolean.
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     *
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     * @serial
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     */
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    private final boolean value;
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    /** use serialVersionUID from JDK 1.0.2 for interoperability */
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    private static final long serialVersionUID = -3665804199014368530L;
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    /**
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     * Allocates a {@code Boolean} object representing the
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     * {@code value} argument.
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     *
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     * <p><b>Note: It is rarely appropriate to use this constructor.
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     * Unless a <i>new</i> instance is required, the static factory
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     * {@link #valueOf(boolean)} is generally a better choice. It is
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     * likely to yield significantly better space and time performance.</b>
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     *
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     * @param   value   the value of the {@code Boolean}.
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     */
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    public Boolean(boolean value) {
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        this.value = value;
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    }
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    /**
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     * Allocates a {@code Boolean} object representing the value
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     * {@code true} if the string argument is not {@code null}
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     * and is equal, ignoring case, to the string {@code "true"}.
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     * Otherwise, allocate a {@code Boolean} object representing the
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     * value {@code false}. Examples:<p>
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     * {@code new Boolean("True")} produces a {@code Boolean} object
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     * that represents {@code true}.<br>
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     * {@code new Boolean("yes")} produces a {@code Boolean} object
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     * that represents {@code false}.
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     *
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     * @param   s   the string to be converted to a {@code Boolean}.
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     */
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    public Boolean(String s) {
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        this(toBoolean(s));
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    }
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    /**
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     * Parses the string argument as a boolean.  The {@code boolean}
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     * returned represents the value {@code true} if the string argument
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     * is not {@code null} and is equal, ignoring case, to the string
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     * {@code "true"}. <p>
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     * Example: {@code Boolean.parseBoolean("True")} returns {@code true}.<br>
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     * Example: {@code Boolean.parseBoolean("yes")} returns {@code false}.
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     *
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     * @param      s   the {@code String} containing the boolean
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     *                 representation to be parsed
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     * @return     the boolean represented by the string argument
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     * @since 1.5
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     */
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    public static boolean parseBoolean(String s) {
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        return toBoolean(s);
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    }
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    /**
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     * Returns the value of this {@code Boolean} object as a boolean
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     * primitive.
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     *
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     * @return  the primitive {@code boolean} value of this object.
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     */
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    public boolean booleanValue() {
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        return value;
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    }
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    /**
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     * Returns a {@code Boolean} instance representing the specified
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     * {@code boolean} value.  If the specified {@code boolean} value
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     * is {@code true}, this method returns {@code Boolean.TRUE};
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     * if it is {@code false}, this method returns {@code Boolean.FALSE}.
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     * If a new {@code Boolean} instance is not required, this method
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     * should generally be used in preference to the constructor
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     * {@link #Boolean(boolean)}, as this method is likely to yield
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     * significantly better space and time performance.
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     *
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     * @param  b a boolean value.
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     * @return a {@code Boolean} instance representing {@code b}.
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     * @since  1.4
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     */
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    public static Boolean valueOf(boolean b) {
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        return (b ? TRUE : FALSE);
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    }
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    /**
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     * Returns a {@code Boolean} with a value represented by the
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     * specified string.  The {@code Boolean} returned represents a
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     * true value if the string argument is not {@code null}
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     * and is equal, ignoring case, to the string {@code "true"}.
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     *
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     * @param   s   a string.
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     * @return  the {@code Boolean} value represented by the string.
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     */
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    public static Boolean valueOf(String s) {
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        return toBoolean(s) ? TRUE : FALSE;
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    }
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    /**
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     * Returns a {@code String} object representing the specified
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     * boolean.  If the specified boolean is {@code true}, then
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     * the string {@code "true"} will be returned, otherwise the
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     * string {@code "false"} will be returned.
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     *
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     * @param b the boolean to be converted
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     * @return the string representation of the specified {@code boolean}
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     * @since 1.4
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     */
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    public static String toString(boolean b) {
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        return b ? "true" : "false";
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    }
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    /**
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     * Returns a {@code String} object representing this Boolean's
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     * value.  If this object represents the value {@code true},
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     * a string equal to {@code "true"} is returned. Otherwise, a
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     * string equal to {@code "false"} is returned.
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     *
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     * @return  a string representation of this object.
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     */
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    public String toString() {
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        return value ? "true" : "false";
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    }
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    /**
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     * Returns a hash code for this {@code Boolean} object.
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     *
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     * @return  the integer {@code 1231} if this object represents
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     * {@code true}; returns the integer {@code 1237} if this
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     * object represents {@code false}.
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     */
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    public int hashCode() {
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        return value ? 1231 : 1237;
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    }
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    /**
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     * Returns {@code true} if and only if the argument is not
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     * {@code null} and is a {@code Boolean} object that
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     * represents the same {@code boolean} value as this object.
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     *
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     * @param   obj   the object to compare with.
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     * @return  {@code true} if the Boolean objects represent the
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     *          same value; {@code false} otherwise.
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     */
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    public boolean equals(Object obj) {
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        if (obj instanceof Boolean) {
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            return value == ((Boolean)obj).booleanValue();
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        }
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        return false;
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    }
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    /**
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     * Returns {@code true} if and only if the system property
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     * named by the argument exists and is equal to the string
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     * {@code "true"}. (Beginning with version 1.0.2 of the
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     * Java<small><sup>TM</sup></small> platform, the test of
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     * this string is case insensitive.) A system property is accessible
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     * through {@code getProperty}, a method defined by the
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     * {@code System} class.
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     * <p>
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     * If there is no property with the specified name, or if the specified
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     * name is empty or null, then {@code false} is returned.
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     *
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     * @param   name   the system property name.
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     * @return  the {@code boolean} value of the system property.
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     * @see     java.lang.System#getProperty(java.lang.String)
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     * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)
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     */
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    public static boolean getBoolean(String name) {
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        boolean result = false;
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        try {
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            result = toBoolean(System.getProperty(name));
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        } catch (IllegalArgumentException e) {
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        } catch (NullPointerException e) {
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        }
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        return result;
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    }
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    /**
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     * Compares this {@code Boolean} instance with another.
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     *
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     * @param   b the {@code Boolean} instance to be compared
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     * @return  zero if this object represents the same boolean value as the
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     *          argument; a positive value if this object represents true
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     *          and the argument represents false; and a negative value if
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     *          this object represents false and the argument represents true
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     * @throws  NullPointerException if the argument is {@code null}
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     * @see     Comparable
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     * @since  1.5
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     */
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    public int compareTo(Boolean b) {
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        return compare(this.value, b.value);
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    }
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    /**
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     * Compares two {@code boolean} values.
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     * The value returned is identical to what would be returned by:
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     * <pre>
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     *    Boolean.valueOf(x).compareTo(Boolean.valueOf(y))
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     * </pre>
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     *
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     * @param  x the first {@code boolean} to compare
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     * @param  y the second {@code boolean} to compare
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     * @return the value {@code 0} if {@code x == y};
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     *         a value less than {@code 0} if {@code !x && y}; and
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     *         a value greater than {@code 0} if {@code x && !y}
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     * @since 1.7
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     */
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    public static int compare(boolean x, boolean y) {
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        return (x == y) ? 0 : (x ? 1 : -1);
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    }
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    private static boolean toBoolean(String name) {
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        return ((name != null) && name.equalsIgnoreCase("true"));
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    }
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}