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/*******************************************************************************
* Copyright (c) 2005, 2008 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.utility.internal;
import java.io.Serializable;
import org.eclipse.jpt.utility.Filter;
/**
* Simple, abstract implementation of <code>Filter</code>
* that holds on to a criterion object that can be used in the
* <code>accept(Object)</code> or <code>reject(Object)</code>
* methods. Subclasses can override either of these methods,
* depending on which is easier to implement. Note that at least
* one of these methods <em>must</em> be overridden or
* an infinite loop will occur. If both of them are overridden,
* only the <code>accept(Object)</code> method will be used.
* <p>
* Simplifies the implementation of straightforward inner classes.
* Here is an example of a filter that can be used by a
* <code>FilteringIterator</code> to return only those strings
* in the nested iterator start with "prefix":
* <pre>
* Filter<String> filter = new SimpleFilter<String>("prefix") {
* public boolean accept(String o) {
* return o.startsWith((String) criterion);
* }
* };
* </pre>
*/
public abstract class SimpleFilter<T, S>
implements Filter<T>, Cloneable, Serializable
{
protected final S criterion;
private static final long serialVersionUID = 1L;
/**
* More useful constructor. The specified criterion can
* be used by a subclass to "accept" or "reject" objects.
*/
protected SimpleFilter(S criterion) {
super();
this.criterion = criterion;
}
/**
* Construct a simple filter with a null criterion
*/
protected SimpleFilter() {
this(null);
}
/**
* Return whether the the specified object should be "rejected".
* The semantics of "rejected" is determined by the client.
*/
protected boolean reject(T o) {
return ! this.accept(o);
}
/**
* Return whether the the specified object should be "accepted".
* The semantics of "accepted" is determined by the client.
*/
public boolean accept(T o) {
return ! this.reject(o);
}
@Override
@SuppressWarnings("unchecked")
public SimpleFilter<T, S> clone() {
try {
return (SimpleFilter<T, S>) super.clone();
} catch (CloneNotSupportedException ex) {
throw new InternalError();
}
}
@Override
public boolean equals(Object o) {
if ( ! (o instanceof SimpleFilter)) {
return false;
}
SimpleFilter<?, ?> other = (SimpleFilter<?, ?>) o;
return (this.criterion == null) ?
(other.criterion == null) : this.criterion.equals(other.criterion);
}
@Override
public int hashCode() {
return (this.criterion == null) ? 0 : this.criterion.hashCode();
}
@Override
public String toString() {
return StringTools.buildToStringFor(this, this.criterion);
}
}
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