com.cedarsoftware.util.SealableList Maven / Gradle / Ivy
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package com.cedarsoftware.util;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.function.Supplier;
/**
* SealableList provides a List or List wrapper that can be 'sealed' and 'unsealed.' When
* sealed, the List is immutable, when unsealed it is mutable. The iterator(),
* listIterator(), and subList() return views that honor the Supplier's sealed state.
* The sealed state can be changed as often as needed.
*
* NOTE: Please do not reformat this code as the current format makes it easy to see the overall structure.
*
* @author John DeRegnaucourt ([email protected])
*
* Copyright (c) Cedar Software LLC
*
* 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
*
* License
*
* 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.
*/
public class SealableList implements List {
private final List list;
private final transient Supplier sealedSupplier;
/**
* Create a SealableList. Since no List is being supplied, this will use an ConcurrentList internally. If you
* want to use an ArrayList for example, use SealableList constructor that takes a List and pass it the instance
* you want it to wrap.
* @param sealedSupplier {@code Supplier} that returns 'true' to indicate sealed, 'false' for mutable.
*/
public SealableList(Supplier sealedSupplier) {
this.list = new ConcurrentList<>();
this.sealedSupplier = sealedSupplier;
}
/**
* Create a SealableList. Since a List is not supplied, the elements from the passed in Collection will be
* copied to an internal ConcurrentList. If you want to use an ArrayList for example, use SealableList
* constructor that takes a List and pass it the instance you want it to wrap.
* @param col Collection to supply initial elements. These are copied to an internal ConcurrentList.
* @param sealedSupplier {@code Supplier} that returns 'true' to indicate sealed, 'false' for mutable.
*/
public SealableList(Collection col, Supplier sealedSupplier) {
this.list = new ConcurrentList<>();
this.list.addAll(col);
this.sealedSupplier = sealedSupplier;
}
/**
* Use this constructor to wrap a List (any kind of List) and make it a SealableList.
* No duplicate of the List is created and the original list is operated on directly if unsealed, or protected
* from changes if sealed.
* @param list List instance to protect.
* @param sealedSupplier {@code Supplier} that returns 'true' to indicate sealed, 'false' for mutable.
*/
public SealableList(List list, Supplier sealedSupplier) {
this.list = list;
this.sealedSupplier = sealedSupplier;
}
private void throwIfSealed() {
if (sealedSupplier.get()) {
throw new UnsupportedOperationException("This list has been sealed and is now immutable");
}
}
// Immutable APIs
public boolean equals(Object other) { return list.equals(other); }
public int hashCode() { return list.hashCode(); }
public String toString() { return list.toString(); }
public int size() { return list.size(); }
public boolean isEmpty() { return list.isEmpty(); }
public boolean contains(Object o) { return list.contains(o); }
public boolean containsAll(Collection col) { return new HashSet<>(list).containsAll(col); }
public int indexOf(Object o) { return list.indexOf(o); }
public int lastIndexOf(Object o) { return list.lastIndexOf(o); }
public T get(int index) { return list.get(index); }
public Object[] toArray() { return list.toArray(); }
public T1[] toArray(T1[] a) { return list.toArray(a);}
public Iterator iterator() { return createSealHonoringIterator(list.iterator()); }
public ListIterator listIterator() { return createSealHonoringListIterator(list.listIterator()); }
public ListIterator listIterator(final int index) { return createSealHonoringListIterator(list.listIterator(index)); }
public List subList(int fromIndex, int toIndex) { return new SealableList<>(list.subList(fromIndex, toIndex), sealedSupplier); }
// Mutable APIs
public boolean add(T t) { throwIfSealed(); return list.add(t); }
public boolean remove(Object o) { throwIfSealed(); return list.remove(o); }
public boolean addAll(Collection col) { throwIfSealed(); return list.addAll(col); }
public boolean addAll(int index, Collection col) { throwIfSealed(); return list.addAll(index, col); }
public boolean removeAll(Collection col) { throwIfSealed(); return list.removeAll(col); }
public boolean retainAll(Collection col) { throwIfSealed(); return list.retainAll(col); }
public void clear() { throwIfSealed(); list.clear(); }
public T set(int index, T element) { throwIfSealed(); return list.set(index, element); }
public void add(int index, T element) { throwIfSealed(); list.add(index, element); }
public T remove(int index) { throwIfSealed(); return list.remove(index); }
private Iterator createSealHonoringIterator(Iterator iterator) {
return new Iterator() {
public boolean hasNext() { return iterator.hasNext(); }
public T next() { return iterator.next(); }
public void remove() { throwIfSealed(); iterator.remove(); }
};
}
private ListIterator createSealHonoringListIterator(ListIterator iterator) {
return new ListIterator() {
public boolean hasNext() { return iterator.hasNext();}
public T next() { return iterator.next(); }
public boolean hasPrevious() { return iterator.hasPrevious(); }
public T previous() { return iterator.previous(); }
public int nextIndex() { return iterator.nextIndex(); }
public int previousIndex() { return iterator.previousIndex(); }
public void remove() { throwIfSealed(); iterator.remove(); }
public void set(T e) { throwIfSealed(); iterator.set(e); }
public void add(T e) { throwIfSealed(); iterator.add(e);}
};
}
}