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/*******************************************************************************
* Copyright (c) 2010 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.internal;
/**
* A <code>NonNullBooleanTransformer</code> will transform a possibly-null
* {@link Boolean} to a non-null {@link Boolean}:<ul>
* <li>When the original {@link Boolean} is <em>not</em> <code>null</code>,
* the transformer will return it unchanged.
* <li>When the original {@link Boolean} is <code>null</code>,
* the transformer will return its client-specified "null value"
* ({@link Boolean#TRUE} or {@link Boolean#FALSE}).
* </ul>
*/
public final class NonNullBooleanTransformer
implements Transformer<Boolean, Boolean>
{
// not null
private final Boolean nullValue;
/**
* A {@link Transformer} that will return the original {@link Boolean} when
* it is non-<code>null</code>; otherwise the {@link Transformer} will return
* {@link Boolean#TRUE}.
*/
public static final Transformer<Boolean, Boolean> TRUE = new NonNullBooleanTransformer(Boolean.TRUE);
/**
* A {@link Transformer} that will return the original {@link Boolean} when
* it is non-<code>null</code>; otherwise the {@link Transformer} will return
* {@link Boolean#FALSE}.
*/
public static final Transformer<Boolean, Boolean> FALSE = new NonNullBooleanTransformer(Boolean.FALSE);
/**
* Return a transformer that will return the specified value if the original
* value is <code>null</code>. Throw a {@link NullPointerException} if the
* specified value is <code>null</code>.
*/
public Transformer<Boolean, Boolean> valueOf(Boolean b) {
return valueOf(b.booleanValue());
}
/**
* Return a transformer that will return the {@link Boolean} corresponding
* to the specified value if the original value is <code>null</code>.
*/
public Transformer<Boolean, Boolean> valueOf(boolean b) {
return b ? TRUE : FALSE;
}
/**
* Ensure only 2 constant versions.
*/
private NonNullBooleanTransformer(Boolean nullValue) {
super();
if (nullValue == null) {
throw new NullPointerException();
}
this.nullValue = nullValue;
}
public Boolean transform(Boolean b) {
return (b != null) ? b : this.nullValue;
}
@Override
public String toString() {
return StringTools.buildToStringFor(this, this.nullValue);
}
}
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