我想知道是否有可能创建一个Java java.util.List,它只允许添加元素但不允许删除元素?
我正在考虑重写删除方法的一种方法。请提出建议。
最佳答案
这可以使用装饰器模式来实现。这样它就可以应用于所有实现 List
的容器:
private static class UnremovableList<E> implements List<E> {
private List<E> innerContainer;
public UnremovableList(List<E> original) {
innerContainer = original
}
@Override
public void add(int location, E object) {
innerContainer.add(location, object);
}
@Override
public boolean add(E object) {
return innerContainer.add(object);
}
@Override
public boolean addAll(int location, Collection<? extends E> collection) {
return innerContainer.addAll(location, collection);
}
@Override
public boolean addAll(Collection<? extends E> collection) {
return innerContainer.addAll(collection);
} -
@Override
public void clear() {
throw new UnsupportedOperationException();
}
@Override
public boolean contains(Object object) {
return innerContainer.contains(object);
}
@Override
public boolean containsAll(Collection<?> collection) {
return innerContainer.containsAll(collection);
}
@Override
public E get(int location) {
return innerContainer.get(location);
}
@Override
public int indexOf(Object object) {
return innerContainer.indexOf(object);
}
@Override
public boolean isEmpty() {
return innerContainer.isEmpty();
}
@NonNull
@Override
public ListIterator<E> listIterator() {
return listIterator(0);
}
@NonNull
@Override
public Iterator<E> iterator() {
return new Iterator<E>() {
Iterator<E> iterator = innerContainer.iterator();
@Override public boolean hasNext() {
return iterator.hasNext();
}
@Override public E next() {
return iterator.next();
}
@Override public void remove() {
throw new UnsupportedOperationException();
}
};
}
@Override
public ListIterator<E> listIterator(final int location) {
return new ListIterator<E>() {
ListIterator<E> iterator = innerContainer.listIterator(location);
@Override public void add(E object) {
throw new UnsupportedOperationException();
}
@Override public boolean hasNext() {
return iterator.hasNext();
}
@Override public boolean hasPrevious() {
return iterator.hasPrevious();
}
@Override public E next() {
return iterator.next();
}
@Override public int nextIndex() {
return iterator.nextIndex();
}
@Override public E previous() {
return iterator.previous();
}
@Override public int previousIndex() {
return iterator.previousIndex();
}
@Override public void remove() {
throw new UnsupportedOperationException();
}
@Override public void set(E object) {
throw new UnsupportedOperationException();
}
};
}
@Override
public int lastIndexOf(Object object) {
return innerContainer.lastIndexOf(object);
}
@Override
public E remove(int location) {
throw new UnsupportedOperationException();
}
@Override
public boolean remove(Object object) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeAll(Collection<?> collection) {
throw new UnsupportedOperationException();
}
@Override
public boolean retainAll(Collection<?> collection) {
throw new UnsupportedOperationException();
}
@Override
public E set(int location, E object) {
return innerContainer.set(location, object);
}
@Override
public int size() {
return innerContainer.size();
}
@NonNull
@Override
public List<E> subList(int start, int end) {
return new UnremovableList(innerContainer.subList(start, end));
}
@NonNull
@Override
public Object[] toArray() {
return innerContainer.toArray();
}
@NonNull
@Override
public <T> T[] toArray(T[] array) {
return innerContainer.toArray(array);
}
}
用法:
List<String> stableList = new UnremovableList(Arrays.asList("A", "B", "C"));
关于Java列表只添加不删除,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/42442965/