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The Boolean.java Java example source code
/*
* Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
* 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
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* 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.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
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
*/
@SuppressWarnings("unchecked")
public static final Class<Boolean> TYPE = (Class) 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>Note: It is rarely appropriate to use this constructor.
* Unless a <i>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.</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(parseBoolean(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 ((s != null) && s.equalsIgnoreCase("true"));
}
/**
* 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 parseBoolean(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}.
*/
@Override
public int hashCode() {
return Boolean.hashCode(value);
}
/**
* Returns a hash code for a {@code boolean} value; compatible with
* {@code Boolean.hashCode()}.
*
* @param value the value to hash
* @return a hash code value for a {@code boolean} value.
* @since 1.8
*/
public static int hashCode(boolean value) {
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>TM 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.
* @throws SecurityException for the same reasons as
* {@link System#getProperty(String) System.getProperty}
* @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 = parseBoolean(System.getProperty(name));
} catch (IllegalArgumentException | 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);
}
/**
* Returns the result of applying the logical AND operator to the
* specified {@code boolean} operands.
*
* @param a the first operand
* @param b the second operand
* @return the logical AND of {@code a} and {@code b}
* @see java.util.function.BinaryOperator
* @since 1.8
*/
public static boolean logicalAnd(boolean a, boolean b) {
return a && b;
}
/**
* Returns the result of applying the logical OR operator to the
* specified {@code boolean} operands.
*
* @param a the first operand
* @param b the second operand
* @return the logical OR of {@code a} and {@code b}
* @see java.util.function.BinaryOperator
* @since 1.8
*/
public static boolean logicalOr(boolean a, boolean b) {
return a || b;
}
/**
* Returns the result of applying the logical XOR operator to the
* specified {@code boolean} operands.
*
* @param a the first operand
* @param b the second operand
* @return the logical XOR of {@code a} and {@code b}
* @see java.util.function.BinaryOperator
* @since 1.8
*/
public static boolean logicalXor(boolean a, boolean b) {
return a ^ b;
}
}
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