com.xiaoleilu.hutool.lang.BoundedPriorityQueue Maven / Gradle / Ivy
package com.xiaoleilu.hutool.lang;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.PriorityQueue;
/**
* 有界优先队列
* 按照给定的排序规则，排序元素，当队列满时，按照给定的排序规则淘汰末尾元素（去除末尾元素）
* @author xiaoleilu
*
* @param 成员类型
*/
public class BoundedPriorityQueue extends PriorityQueue{
private static final long serialVersionUID = 3794348988671694820L;
//容量
private int capacity;
private Comparator comparator;
public BoundedPriorityQueue(int capacity) {
this(capacity, null);
}
/**
* 构造
* @param capacity 容量
* @param comparator 比较器
*/
public BoundedPriorityQueue(int capacity, final Comparator comparator) {
super(capacity, new Comparator(){
@Override
public int compare(E o1, E o2) {
int cResult = 0;
if(comparator != null) {
cResult = comparator.compare(o1, o2);
}else {
@SuppressWarnings("unchecked")
Comparable o1c = (Comparable)o1;
cResult = o1c.compareTo(o2);
}
return - cResult;
}
});
this.capacity = capacity;
this.comparator = comparator;
}
/**
* 加入元素，当队列满时，淘汰末尾元素
* @param e 元素
* @return 加入成功与否
*/
@Override
public boolean offer(E e) {
if(size() >= capacity) {
E head = peek();
if (this.comparator().compare(e, head) <= 0){
return true;
}
//当队列满时，就要淘汰顶端队列
poll();
}
return super.offer(e);
}
/**
* 添加多个元素
* 参数为集合的情况请使用{@link PriorityQueue#addAll}
* @param c 元素数组
* @return 是否发生改变
*/
public boolean addAll(E[] c) {
return this.addAll(Arrays.asList(c));
}
/**
* @return 返回排序后的列表
*/
public ArrayList toList() {
final ArrayList list = new ArrayList(this);
Collections.sort(list, comparator);
return list;
}
@Override
public Iterator iterator() {
return toList().iterator();
}
}