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/*******************************************************************************
* Copyright (c) 2010, 2012 Oracle. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0, which accompanies this distribution
* and is available at http://www.eclipse.org/legal/epl-v10.html.
*
* Contributors:
* Oracle - initial API and implementation
******************************************************************************/
package org.eclipse.jpt.common.utility;
import java.io.Serializable;
/**
* Interface for a container for holding a <code>boolean</code> that cannot be
* changed by clients.
* <p>
* Provisional API: This interface is part of an interim API that is still
* under development and expected to change significantly before reaching
* stability. It is available at this early stage to solicit feedback from
* pioneering adopters on the understanding that any code that uses this API
* will almost certainly be broken (repeatedly) as the API evolves.
*/
public interface BooleanReference {
/**
* Return the current <code>boolean</code> value.
*/
boolean getValue();
/**
* Return whether the current <code>boolean</code> value is equal to the
* specified value.
*/
boolean is(boolean value);
/**
* Return whether the current <code>boolean</code> value is not equal to
* the specified value.
*/
boolean isNot(boolean value);
/**
* Return whether the current <code>boolean</code> value is
* <code>true</code>.
*/
boolean isTrue();
/**
* Return whether the current <code>boolean</code> value is
* <code>false</code>.
*/
boolean isFalse();
/**
* Convenience method.
*/
final class Value {
public static BooleanReference of(boolean value) {
return value ? True.instance() : False.instance();
}
}
/**
* Singleton implementation of the read-only boolean reference interface
* whose value is always <code>true</code>.
*/
final class True
implements BooleanReference, Serializable
{
public static final BooleanReference INSTANCE = new True();
public static BooleanReference instance() {
return INSTANCE;
}
// ensure single instance
private True() {
super();
}
public boolean getValue() {
return true;
}
public boolean is(boolean value) {
return value;
}
public boolean isNot(boolean value) {
return ! value;
}
public boolean isTrue() {
return true;
}
public boolean isFalse() {
return false;
}
@Override
public String toString() {
return "[true]"; //$NON-NLS-1$
}
private static final long serialVersionUID = 1L;
private Object readResolve() {
// replace this object with the singleton
return INSTANCE;
}
}
/**
* Singleton implementation of the read-only boolean reference interface
* whose value is always <code>false</code>.
*/
final class False
implements BooleanReference, Serializable
{
public static final BooleanReference INSTANCE = new False();
public static BooleanReference instance() {
return INSTANCE;
}
// ensure single instance
private False() {
super();
}
public boolean getValue() {
return false;
}
public boolean is(boolean value) {
return ! value;
}
public boolean isNot(boolean value) {
return value;
}
public boolean isTrue() {
return false;
}
public boolean isFalse() {
return false;
}
@Override
public String toString() {
return "[false]"; //$NON-NLS-1$
}
private static final long serialVersionUID = 1L;
private Object readResolve() {
// replace this object with the singleton
return INSTANCE;
}
}
}
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