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EmptyChain.java
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package soot.util;
/*-
* #%L
* Soot - a J*va Optimization Framework
* %%
* Copyright (C) 1997 - 2018 Raja Vallée-Rai and others
* %%
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 2.1 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Lesser Public License for more details.
*
* You should have received a copy of the GNU General Lesser Public
* License along with this program. If not, see
* <http://www.gnu.org/licenses/lgpl-2.1.html>.
* #L%
*/
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
/**
* Class representing an unmodifiable empty chain
*
* @author Steven Arzt
*
* @param <T>
*/
public class EmptyChain<T> implements Chain<T> {
private static final long serialVersionUID = 1675685752701192002L;
// Lazy initialized singleton
private static class EmptyIteratorSingleton {
static final Iterator<Object> INSTANCE = new Iterator<Object>() {
@Override
public boolean hasNext() {
return false;
}
@Override
public Object next() {
throw new NoSuchElementException();
}
@Override
public void remove() {
throw new NoSuchElementException();
}
};
}
private static <X> Iterator<X> emptyIterator() {
@SuppressWarnings("unchecked")
Iterator<X> retVal = (Iterator<X>) EmptyIteratorSingleton.INSTANCE;
return retVal;
}
// Lazy initialized singleton
private static class EmptyChainSingleton {
static final EmptyChain<Object> INSTANCE = new EmptyChain<Object>();
}
public static <X> EmptyChain<X> v() {
@SuppressWarnings("unchecked")
EmptyChain<X> retVal = (EmptyChain<X>) EmptyChainSingleton.INSTANCE;
return retVal;
}
@Override
public String toString() {
return "[]";
}
@Override
public boolean isEmpty() {
return true;
}
@Override
public boolean contains(Object o) {
return false;
}
@Override
public Object[] toArray() {
return new Object[0];
}
@Override
public <X> X[] toArray(X[] a) {
@SuppressWarnings("unchecked")
X[] retVal = (X[]) new Object[0];
return retVal;
}
@Override
public boolean add(T e) {
throw new RuntimeException("Cannot add elements to an unmodifiable chain");
}
@Override
public boolean containsAll(Collection<?> c) {
return false;
}
@Override
public boolean addAll(Collection<? extends T> c) {
throw new RuntimeException("Cannot add elements to an unmodifiable chain");
}
@Override
public boolean removeAll(Collection<?> c) {
throw new RuntimeException("Cannot remove elements from an unmodifiable chain");
}
@Override
public boolean retainAll(Collection<?> c) {
throw new RuntimeException("Cannot add elements to an unmodifiable chain or remove ones from such chain");
}
@Override
public void clear() {
throw new RuntimeException("Cannot remove elements from an unmodifiable chain");
}
@Override
public void insertBefore(List<T> toInsert, T point) {
throw new RuntimeException("Cannot add elements to an unmodifiable chain");
}
@Override
public void insertAfter(List<T> toInsert, T point) {
throw new RuntimeException("Cannot add elements to an unmodifiable chain");
}
@Override
public void insertAfter(T toInsert, T point) {
throw new RuntimeException("Cannot add elements to an unmodifiable chain");
}
@Override
public void insertBefore(T toInsert, T point) {
throw new RuntimeException("Cannot add elements to an unmodifiable chain");
}
@Override
public void insertBefore(Chain<T> toInsert, T point) {
throw new RuntimeException("Cannot add elements to an unmodifiable chain");
}
@Override
public void insertAfter(Chain<T> toInsert, T point) {
throw new RuntimeException("Cannot add elements to an unmodifiable chain");
}
@Override
public void swapWith(T out, T in) {
throw new RuntimeException("Cannot replace elements in an unmodifiable chain");
}
@Override
public boolean remove(Object u) {
throw new RuntimeException("Cannot remove elements from an unmodifiable chain");
}
@Override
public void addFirst(T u) {
throw new RuntimeException("Cannot add elements to an unmodifiable chain");
}
@Override
public void addLast(T u) {
throw new RuntimeException("Cannot add elements to an unmodifiable chain");
}
@Override
public void removeFirst() {
throw new RuntimeException("Cannot remove elements from an unmodifiable chain");
}
@Override
public void removeLast() {
throw new RuntimeException("Cannot remove elements from an unmodifiable chain");
}
@Override
public boolean follows(T someObject, T someReferenceObject) {
return false;
}
@Override
public T getFirst() {
throw new NoSuchElementException();
}
@Override
public T getLast() {
throw new NoSuchElementException();
}
@Override
public T getSuccOf(T point) {
throw new NoSuchElementException();
}
@Override
public T getPredOf(T point) {
throw new NoSuchElementException();
}
@Override
public Iterator<T> snapshotIterator() {
return emptyIterator();
}
@Override
public Iterator<T> iterator() {
return emptyIterator();
}
@Override
public Iterator<T> iterator(T u) {
return emptyIterator();
}
@Override
public Iterator<T> iterator(T head, T tail) {
return emptyIterator();
}
@Override
public int size() {
return 0;
}
@Override
public long getModificationCount() {
return 0;
}
@Override
public Collection<T> getElementsUnsorted() {
return Collections.emptyList();
}
@Override
public void insertAfter(Collection<? extends T> toInsert, T point) {
throw new RuntimeException("Cannot add elements to an unmodifiable chain");
}
@Override
public void insertBefore(Collection<? extends T> toInsert, T point) {
throw new RuntimeException("Cannot add elements to an unmodifiable chain");
}
}