Java 中的 PriorityQueue remove()方法
原文:https://www . geesforgeks . org/priorityqueue-remove-method-in-Java/
的 PriorityQueue 类Java . util 包 的 remove()方法用于从 PriorityQueue 中移除特定元素。众所周知，进入优先级队列时的元素没有被排序，但是众所周知，从优先级队列中取出元素时，元素总是被排序，这是优先级队列的一个特征。这里，数据类型的元素优先级的默认顺序定义如下:
- 整数:最先出现的最小元素(只处理正数时)
- 字符串:字母顺序
注意:我们还可以在创建这个类的实例时插入一个比较器，告诉我们应该如何定义优先级。
语法:
PriorityQueue<String> = new PriorityQueue<String>(ComparatorHere);
语法:移除方法
Priority_Queue.remove(Object O)
参数:参数 O 属于优先级队列类型，指定要从优先级队列中删除的元素。
返回值:如果队列中存在指定的元素，该方法返回真，否则返回假。
例 1
Java 语言(一种计算机语言，尤用于创建网站)
// Java Program to Illustrate remove() Method
// in PriorityQueue
// Where Elements are of String Type
// Importing all utility classes
import java.util.*;
// Main class
// PriorityQueueDemo
public class GFG {
// Main driver method
public static void main(String args[])
{
// Creating an empty PriorityQueue
// where elements are of string type
PriorityQueue<String> queue
= new PriorityQueue<String>();
// Adding elements into the Queue
// using add() method
queue.add("Welcome");
queue.add("To");
queue.add("Geeks");
queue.add("For");
queue.add("Geeks");
// Printing the elements of PriorityQueue
System.out.println("Initial PriorityQueue: "
+ queue);
// Removing elements from PriorityQueue
// using remove() method
queue.remove("Geeks");
queue.remove("For");
queue.remove("Welcome");
// Displaying the PriorityQueue
// after removal of element
System.out.println("PriorityQueue after removing "
+ "elements: " + queue);
}
}
Output
Initial PriorityQueue: [For, Geeks, To, Welcome, Geeks]
PriorityQueue after removing elements: [Geeks, To]
例 2
Java 语言(一种计算机语言，尤用于创建网站)
// Java Program to Illustrate remove() Method
// of PriorityQueue class
// Where Elements are of Integer type
// Importing required classes
import java.util.*;
// Main class
// PriorityQueueDemo
public class GFG {
// Main driver method
public static void main(String args[])
{
// Creating an empty PriorityQueue by
// creating an object of integer type
PriorityQueue<Integer> queue
= new PriorityQueue<Integer>();
// Adding custom input elements
// using add() method
queue.add(10);
queue.add(15);
queue.add(30);
queue.add(20);
queue.add(5);
// Displaying the PriorityQueue
System.out.println("Initial PriorityQueue: "
+ queue);
// Removing elements from the PriorityQueue
// using remove() method
queue.remove(30);
queue.remove(5);
// Displaying the PriorityQueue elements
// after removal
System.out.println("PriorityQueue after removing "
+ "elements: " + queue);
}
}
Output:
Initial PriorityQueue: [5, 10, 30, 20, 15]
PriorityQueue after removing elements: [10, 20, 15]
Geek，你有没有想过如果 remove()方法的调用超过了队列中存在的元素，会发生什么？在这种情况下，它将继续删除那里的元素，此后它将找不到任何元素来优先删除，因此它将抛出一个异常，如下所示。
注意:这个类确实实现了 AbstractQueueInterface
例
Java 语言(一种计算机语言，尤用于创建网站)
// Java Program to illustrate remove() Method
// in PriorityQueue
// Where Exception is encountered
// Importing required classes
import java.io.*;
import java.util.PriorityQueue;
// Main class
// PriorityQueueException
class GFG {
// Main driver method
public static void main(String[] args)
{
// Creating an empty PriorityQueue
PriorityQueue<Integer> pq
= new PriorityQueue<Integer>();
// Note: Elements are inserted in unsorted order in
// priority queue but after removal of elements
// queue is always sorted.
// Adding elements in above queue
// using add() method
pq.add(2);
pq.add(14);
pq.add(41);
pq.add(7);
pq.add(99);
// Elements in queue are unsorted by far
// Getting size of above queue before deletion
// of any element using size() method
System.out.println(
"Size of priority queue before deletion : "
+ pq.size());
// Printing all elements of above queue
System.out.println(
"Priority queue before removal : " + pq);
// Calling remove() method over priority queue
// in which there were 5 elements
// Here calling remove() method say be it 2 times
// So 2 top priority elements will be removed
System.out.println(" 1st element removed : "
+ pq.remove());
System.out.println(" 2nd element removed : "
+ pq.remove());
System.out.println(" 3rd element removed : "
+ pq.remove());
System.out.println(" 4th element removed : "
+ pq.remove());
System.out.println(" 5th element removed : "
+ pq.remove());
// By now queue is empty and if now we made further
// remove() call it will throw exception for this
System.out.println(" 6th element removed : "
+ pq.remove());
// As we know smaller the integer bigger the
// priority been set by default comparator of this
// class
// Note: Now the element is always returned sorted
// from a priority queue is a trait of this class
// Printing the queue after removal of priority
// elements
System.out.println(
"Priority queue after removal as follows: "
+ pq);
}
}
输出:
输出解释:
它展示了队列中已经没有其他元素了，因为队列现在是空的，所以它抛出了 NoSuchElementException 。
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