jlibs.core.util.AbstractIterator Maven / Gradle / Ivy
/**
* Copyright 2015 Santhosh Kumar Tekuri
*
* The JLibs authors license this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package jlibs.core.util;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* Abstract Implementation of Iterator. Subclass need to override
* only computeNext() method.
*
* @author Santhosh Kumar T
*/
public abstract class AbstractIterator implements Iterator{
protected static final Object NO_MORE_ELEMENTS = new Object();
private Object next;
protected abstract Object computeNext();
protected AbstractIterator reset(){
next = null;
return this;
}
@Override
public final boolean hasNext(){
if(next==NO_MORE_ELEMENTS)
return false;
if(next==null)
next = computeNext();
return next!=NO_MORE_ELEMENTS;
}
@Override
@SuppressWarnings({"unchecked"})
public final T next(){
if(hasNext()){
T current = (T)next;
next = null;
return current;
}else
throw new NoSuchElementException();
}
@Override
public void remove(){
throw new UnsupportedOperationException();
}
}