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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * particular file as subject to the "Classpath" exception as provided

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 */

package java.lang;

/**

 * The Boolean class wraps a value of the primitive type

 * {@code boolean} in an object. An object of type

 * {@code Boolean} contains a single field whose type is

 * {@code boolean}.

 * <p>

 * In addition, this class provides many methods for

 * converting a {@code boolean} to a {@code String} and a

 * {@code String} to a {@code boolean}, as well as other

 * constants and methods useful when dealing with a

 * {@code boolean}.

 *

 * @author  Arthur van Hoff

 * @since   JDK1.0

 */

public final class Boolean implements java.io.Serializable,

                                      Comparable<Boolean>

{

    /**

     * The {@code Boolean} object corresponding to the primitive

     * value {@code true}.

     */

    public static final Boolean TRUE = new Boolean(true);

    /**

     * The {@code Boolean} object corresponding to the primitive

     * value {@code false}.

     */

    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} object representing the

     * {@code value} argument.

     *

     * <p><b>Note: It is rarely appropriate to use this constructor.

     * Unless a <i>new</i> 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.</b>

     *

     * @param   value   the value of the {@code Boolean}.

     */

    public Boolean(boolean value) {

        this.value = value;

    }

    /**

     * Allocates a {@code Boolean} object representing the value

     * {@code true} if the string argument is not {@code null}

     * and is equal, ignoring case, to the string {@code "true"}.

     * Otherwise, allocate a {@code Boolean} object representing the

     * value {@code false}. Examples:<p>

     * {@code new Boolean("True")} produces a {@code Boolean} object

     * that represents {@code true}.<br>

     * {@code new Boolean("yes")} produces a {@code Boolean} object

     * that represents {@code false}.

     *

     * @param   s   the string to be converted to a {@code Boolean}.

     */

    public Boolean(String s) {

        this(toBoolean(s));

    }

    /**

     * Parses the string argument as a boolean.  The {@code boolean}

     * returned represents the value {@code true} if the string argument

     * is not {@code null} and is equal, ignoring case, to the string

     * {@code "true"}. <p>

     * Example: {@code Boolean.parseBoolean("True")} returns {@code true}.<br>

     * Example: {@code Boolean.parseBoolean("yes")} returns {@code false}.

     *

     * @param      s   the {@code String} 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 {@code Boolean} object as a boolean

     * primitive.

     *

     * @return  the primitive {@code boolean} value of this object.

     */

    public boolean booleanValue() {

        return value;

    }

    /**

     * Returns a {@code Boolean} instance representing the specified

     * {@code boolean} value.  If the specified {@code boolean} value

     * is {@code true}, this method returns {@code Boolean.TRUE};

     * if it is {@code false}, this method returns {@code Boolean.FALSE}.

     * If a new {@code Boolean} 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 {@code Boolean} instance representing {@code b}.

     * @since  1.4

     */

    public static Boolean valueOf(boolean b) {

        return (b ? TRUE : FALSE);

    }

    /**

     * Returns a {@code Boolean} with a value represented by the

     * specified string.  The {@code Boolean} returned represents a

     * true value if the string argument is not {@code null}

     * and is equal, ignoring case, to the string {@code "true"}.

     *

     * @param   s   a string.

     * @return  the {@code Boolean} value represented by the string.

     */

    public static Boolean valueOf(String s) {

        return toBoolean(s) ? TRUE : FALSE;

    }

    /**

     * Returns a {@code String} object representing the specified

     * boolean.  If the specified boolean is {@code true}, 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}

     * @since 1.4

     */

    public static String toString(boolean b) {

        return b ? "true" : "false";

    }

    /**

     * Returns a {@code String} object representing this Boolean's

     * value.  If this object represents the value {@code true},

     * 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 {@code Boolean} object.

     *

     * @return  the integer {@code 1231} if this object represents

     * {@code true}; returns the integer {@code 1237} if this

     * object represents {@code false}.

     */

    public int hashCode() {

        return value ? 1231 : 1237;

    }

    /**

     * Returns {@code true} if and only if the argument is not

     * {@code null} and is a {@code Boolean} object that

     * represents the same {@code boolean} value as this object.

     *

     * @param   obj   the object to compare with.

     * @return  {@code true} if the Boolean objects represent the

     *          same value; {@code false} otherwise.

     */

    public boolean equals(Object obj) {

        if (obj instanceof Boolean) {

            return value == ((Boolean)obj).booleanValue();

        }

        return false;

    }

    /**

     * Returns {@code true} 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

     * Java<small><sup>TM</sup></small> platform, the test of

     * this string is case insensitive.) A system property is accessible

     * through {@code getProperty}, a method defined by the

     * {@code System} class.

     * <p>

     * If there is no property with the specified name, or if the specified

     * name is empty or null, then {@code false} is returned.

     *

     * @param   name   the system property name.

     * @return  the {@code boolean} 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 {@code Boolean} instance with another.

     *

     * @param   b the {@code Boolean} 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 {@code null}

     * @see     Comparable

     * @since  1.5

     */

    public int compareTo(Boolean b) {

        return compare(this.value, b.value);

    }

    /**

     * Compares two {@code boolean} values.

     * The value returned is identical to what would be returned by:

     * <pre>

     *    Boolean.valueOf(x).compareTo(Boolean.valueOf(y))

     * </pre>

     *

     * @param  x the first {@code boolean} to compare

     * @param  y the second {@code boolean} to compare

     * @return the value {@code 0} if {@code x == y};

     *         a value less than {@code 0} if {@code !x && y}; and

     *         a value greater than {@code 0} if {@code x && !y}

     * @since 1.7

     */

    public static int compare(boolean x, boolean y) {

        return (x == y) ? 0 : (x ? 1 : -1);

    }

    private static boolean toBoolean(String name) {

        return ((name != null) && name.equalsIgnoreCase("true"));

    }

}