Java ConcurrentLinkedDeque peek()用法及代碼示例

Java中的java.util.ConcurrentLinkedDeque.peek()方法用於檢索或獲取Deque頭部的元素。檢索到的元素不會從Deque中刪除或刪除，而是方法僅返回它。如果雙端隊列中沒有元素，則返回Null。

用法:

Array_Deque.peek()

參數：該方法不帶任何參數。

返回值：該方法返回雙端隊列頂部的元素。

以下程序說明了Java.util.ConcurrentLinkedDeque.peek()方法：

示例1:

// Java code to illustrate peek() 
  
import java.util.concurrent.*; 
  
public class ConcurrentLinkedDequeDemo { 
    public static void main(String args[]) 
    { 
        // Creating an empty ConcurrentLinkedDeque 
        ConcurrentLinkedDeque<String> de_que 
            = new ConcurrentLinkedDeque<String>(); 
  
        // Use add() method to add elements into the Deque 
        de_que.add("Welcome"); 
        de_que.add("To"); 
        de_que.add("Geeks"); 
        de_que.add("4"); 
        de_que.add("Geeks"); 
  
        // Displaying the ConcurrentLinkedDeque 
        System.out.println("Initial ConcurrentLinkedDeque: "
                           + de_que); 
  
        // Displaying the head 
        System.out.println("The element at head is: "
                           + de_que.peek()); 
  
        // Displaying the ConcurrentLinkedDeque after operation 
        System.out.println("Final ConcurrentLinkedDeque: "
                           + de_que); 
    } 
}

輸出：

Initial ConcurrentLinkedDeque: [Welcome, To, Geeks, 4, Geeks]
The element at head is: Welcome
Final ConcurrentLinkedDeque: [Welcome, To, Geeks, 4, Geeks]

示例2:

// Java code to illustrate peek() 
import java.util.concurrent.*; 
  
public class ConcurrentLinkedDequeDemo { 
    public static void main(String args[]) 
    { 
        // Creating an empty ConcurrentLinkedDeque 
        ConcurrentLinkedDeque<Integer> de_que 
            = new ConcurrentLinkedDeque<Integer>(); 
  
        // Use add() method to add elements into the Deque 
        de_que.add(10); 
        de_que.add(15); 
        de_que.add(30); 
        de_que.add(20); 
        de_que.add(5); 
  
        // Displaying the ConcurrentLinkedDeque 
        System.out.println("Initial ConcurrentLinkedDeque: "
                           + de_que); 
  
        // Displaying the head 
        System.out.println("The element at head is: "
                           + de_que.peek()); 
  
        // Displaying the ConcurrentLinkedDeque after operation 
        System.out.println("Final ConcurrentLinkedDeque: "
                           + de_que); 
    } 
}

輸出：

Initial ConcurrentLinkedDeque: [10, 15, 30, 20, 5]
The element at head is: 10
Final ConcurrentLinkedDeque: [10, 15, 30, 20, 5]

示例3:對於空的雙端隊列：

// Java code to illustrate peek() 
import java.util.concurrent.*; 
  
public class ConcurrentLinkedDequeDemo { 
    public static void main(String args[]) 
    { 
        // Creating an empty ConcurrentLinkedDeque 
        ConcurrentLinkedDeque<Integer> de_que 
            = new ConcurrentLinkedDeque<Integer>(); 
  
        // Displaying the ConcurrentLinkedDeque 
        System.out.println("ConcurrentLinkedDeque: "
                           + de_que); 
  
        // Displaying the head 
        System.out.println("The element at head is: "
                           + de_que.peek()); 
    } 
}

輸出：

ConcurrentLinkedDeque: []
The element at head is: null

相關用法

注：本文由純淨天空篩選整理自MerlynShelley大神的英文原創作品 ConcurrentLinkedDeque peek() method in Java with Example。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。