/*
* @(#)Boolean.java 1.51 04/05/11
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN 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>.
* <p>
* 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 1.51, 05/11/04
* @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.
*
* <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</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"</code>.
* Otherwise, allocate a <code>Boolean</code> object representing the
* value <code>false</code>. Examples:<p>
* <tt>new Boolean("True")</tt> produces a <tt>Boolean</tt> object
* that represents <tt>true</tt>.<br>
* <tt>new Boolean("yes")</tt> 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"</code>.
*
* @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 the
* value <code>true</code> if the string argument is not <code>null</code>
* and is equal, ignoring case, to the string <code>"true"</code>. <p>
* Example: <tt>Boolean.valueOf("True")</tt> returns <tt>true</tt>.<br>
* Example: <tt>Boolean.valueOf("yes")</tt> returns <tt>false</tt>.
*
* @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 <tt>"true"</tt> will be returned, otherwise the
* string <tt>"false"</tt> 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"</code> is returned. Otherwise, a
* string equal to <code>"false"</code> 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"</code>. (Beginning with version 1.0.2 of the
* Java<font size="-2"><sup>TM</sup></font> 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.
* <p>
* 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"));
}
}
|
