/*
* Copyright 2014 Red Hat, Inc. and/or its affiliates.
*
* Licensed 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 org.optaplanner.core.impl.heuristic.selector.common.iterator;
import java.util.ListIterator;
import java.util.NoSuchElementException;
public class SingletonIterator<T> implements ListIterator<T> {
private final T singleton;
private boolean hasNext;
private boolean hasPrevious;
public SingletonIterator(T singleton) {
this.singleton = singleton;
hasNext = true;
hasPrevious = true;
}
public SingletonIterator(T singleton, int index) {
this.singleton = singleton;
if (index < 0 || index > 1) {
throw new IllegalArgumentException("The index (" + index + ") is invalid.");
}
hasNext = (index == 0);
hasPrevious = !hasNext;
}
@Override
public boolean hasNext() {
return hasNext;
}
@Override
public T next() {
if (!hasNext) {
throw new NoSuchElementException();
}
hasNext = false;
hasPrevious = true;
return singleton;
}
@Override
public boolean hasPrevious() {
return hasPrevious;
}
@Override
public T previous() {
if (!hasPrevious) {
throw new NoSuchElementException();
}
hasNext = true;
hasPrevious = false;
return singleton;
}
@Override
public int nextIndex() {
return hasNext ? 0 : 1;
}
@Override
public int previousIndex() {
return hasPrevious ? 0 : -1;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
@Override
public void set(T t) {
throw new UnsupportedOperationException();
}
@Override
public void add(T t) {
throw new UnsupportedOperationException();
}
}