com.vaadin.data.util.ListSet Maven / Gradle / Ivy
/*
* Vaadin Framework 7
*
* Copyright (C) 2000-2024 Vaadin Ltd
*
* This program is available under Vaadin Commercial License and Service Terms.
*
* See for the full
* license.
*/
package com.vaadin.data.util;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
/**
* ListSet is an internal Vaadin class which implements a combination of a List
* and a Set. The main purpose of this class is to provide a list with a fast
* {@link #contains(Object)} method. Each inserted object must by unique (as
* specified by {@link #equals(Object)}). The {@link #set(int, Object)} method
* allows duplicates because of the way {@link Collections#sort(java.util.List)}
* works.
*
* This class is subject to change and should not be used outside Vaadin core.
*/
public class ListSet extends ArrayList {
private HashSet itemSet = null;
/**
* Contains a map from an element to the number of duplicates it has. Used
* to temporarily allow duplicates in the list.
*/
private HashMap duplicates = new HashMap();
public ListSet() {
super();
itemSet = new HashSet();
}
public ListSet(Collection c) {
super(c);
itemSet = new HashSet(c.size());
itemSet.addAll(c);
}
public ListSet(int initialCapacity) {
super(initialCapacity);
itemSet = new HashSet(initialCapacity);
}
// Delegate contains operations to the set
@Override
public boolean contains(Object o) {
return itemSet.contains(o);
}
@Override
public boolean containsAll(Collection c) {
return itemSet.containsAll(c);
}
// Methods for updating the set when the list is updated.
@Override
public boolean add(E e) {
if (contains(e)) {
// Duplicates are not allowed
return false;
}
if (super.add(e)) {
itemSet.add(e);
return true;
} else {
return false;
}
}
/**
* Works as java.util.ArrayList#add(int, java.lang.Object) but returns
* immediately if the element is already in the ListSet.
*/
@Override
public void add(int index, E element) {
if (contains(element)) {
// Duplicates are not allowed
return;
}
super.add(index, element);
itemSet.add(element);
}
@Override
public boolean addAll(Collection c) {
boolean modified = false;
Iterator i = c.iterator();
while (i.hasNext()) {
E e = i.next();
if (contains(e)) {
continue;
}
if (add(e)) {
itemSet.add(e);
modified = true;
}
}
return modified;
}
@Override
public boolean addAll(int index, Collection c) {
ensureCapacity(size() + c.size());
boolean modified = false;
Iterator i = c.iterator();
while (i.hasNext()) {
E e = i.next();
if (contains(e)) {
continue;
}
add(index++, e);
itemSet.add(e);
modified = true;
}
return modified;
}
@Override
public void clear() {
super.clear();
itemSet.clear();
}
@Override
public int indexOf(Object o) {
if (!contains(o)) {
return -1;
}
return super.indexOf(o);
}
@Override
public int lastIndexOf(Object o) {
if (!contains(o)) {
return -1;
}
return super.lastIndexOf(o);
}
@Override
public E remove(int index) {
E e = super.remove(index);
if (e != null) {
itemSet.remove(e);
}
return e;
}
@Override
public boolean remove(Object o) {
if (super.remove(o)) {
itemSet.remove(o);
return true;
} else {
return false;
}
}
@Override
protected void removeRange(int fromIndex, int toIndex) {
HashSet toRemove = new HashSet();
for (int idx = fromIndex; idx < toIndex; idx++) {
toRemove.add(get(idx));
}
super.removeRange(fromIndex, toIndex);
itemSet.removeAll(toRemove);
}
@Override
public E set(int index, E element) {
if (contains(element)) {
// Element already exist in the list
if (get(index) == element) {
// At the same position, nothing to be done
return element;
} else {
// Adding at another position. We assume this is a sort
// operation and temporarily allow it.
// We could just remove (null) the old element and keep the list
// unique. This would require finding the index of the old
// element (indexOf(element)) which is not a fast operation in a
// list. So we instead allow duplicates temporarily.
addDuplicate(element);
}
}
E old = super.set(index, element);
removeFromSet(old);
itemSet.add(element);
return old;
}
/**
* Removes "e" from the set if it no longer exists in the list.
*
* @param e
*/
private void removeFromSet(E e) {
Integer dupl = duplicates.get(e);
if (dupl != null) {
// A duplicate was present so we only decrement the duplicate count
// and continue
if (dupl == 1) {
// This is what always should happen. A sort sets the items one
// by one, temporarily breaking the uniqueness requirement.
duplicates.remove(e);
} else {
duplicates.put(e, dupl - 1);
}
} else {
// The "old" value is no longer in the list.
itemSet.remove(e);
}
}
/**
* Marks the "element" can be found more than once from the list. Allowed in
* {@link #set(int, Object)} to make sorting work.
*
* @param element
*/
private void addDuplicate(E element) {
Integer nr = duplicates.get(element);
if (nr == null) {
nr = 1;
} else {
nr++;
}
/*
* Store the number of duplicates of this element so we know later on if
* we should remove an element from the set or if it was a duplicate (in
* removeFromSet)
*/
duplicates.put(element, nr);
}
@SuppressWarnings("unchecked")
@Override
public Object clone() {
ListSet v = (ListSet) super.clone();
v.itemSet = new HashSet(itemSet);
return v;
}
}