Java 中的 PriorityQueue peek()方法
原文:https://www . geeksforgeeks . org/priorityqueue-peek-method-in-Java/
java 中的 java.util.PriorityQueue.peek()方法用于检索或获取 Queue 的第一个元素或位于 Queue 头部的元素。检索到的元素不会被删除或从队列中移除。
语法:
Priority_Queue.peek()
参数:该方法不取任何参数。
返回值:该方法返回队列头部的元素，否则如果队列为空，则返回空。
下面的程序说明了 java.util.PriorityQueue.peek()方法: 程序 1:
// Java code to illustrate peek()
import java.util.*;
public class PriorityQueueDemo {
public static void main(String args[])
{
// Creating an empty PriorityQueue
PriorityQueue<String> queue = new PriorityQueue<String>();
// Use add() method to add elements into the Queue
queue.add("Welcome");
queue.add("To");
queue.add("Geeks");
queue.add("For");
queue.add("Geeks");
// Displaying the PriorityQueue
System.out.println("Initial PriorityQueue: " + queue);
// Fetching the element at the head of the queue
System.out.println("The element at the head of the"
+ " queue is: " + queue.peek());
// Displaying the Queue after the Operation
System.out.println("Final PriorityQueue: " + queue);
}
}
Output:
Initial PriorityQueue: [For, Geeks, To, Welcome, Geeks]
The element at the head of the queue is: For
Final PriorityQueue: [For, Geeks, To, Welcome, Geeks]
程序 2:
// Java code to illustrate peek()
import java.util.*;
public class PriorityQueueDemo {
public static void main(String args[])
{
// Creating an empty PriorityQueue
PriorityQueue<Integer> queue = new PriorityQueue<Integer>();
// Use add() method to add elements into the Queue
queue.add(10);
queue.add(15);
queue.add(30);
queue.add(20);
queue.add(5);
// Displaying the PriorityQueue
System.out.println("Initial PriorityQueue: " + queue);
// Fetching the element at the head of the queue
System.out.println("The element at the head of the"
+ " queue is: " + queue.peek());
// Displaying the Queue after the Operation
System.out.println("Final PriorityQueue: " + queue);
}
}
Output:
Initial PriorityQueue: [5, 10, 30, 20, 15]
The element at the head of the queue is: 5
Final PriorityQueue: [5, 10, 30, 20, 15]
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