Java LinkedBlockingDeque getFirst()用法及代碼示例

LinkedBlockingDeque的getFirst()方法返回Deque容器中最前麵的元素。如果LinkedBlockingDeque為空，則在函數調用時將返回NoSuchElementException。

用法:

public E getLast()

參數：此方法不接受任何參數。

返回值：此方法返回此Deque容器的第一個元素或頭。

異常：當雙端隊列為空時，該函數僅引發一個異常，即NoSuchElementException

以下示例程序旨在說明LinkedBlockingDeque的getFirst()方法：

示例1:

// Java Program Demonstrate getFirst() 
// method of LinkedBlockingDeque 
  
import java.util.concurrent.LinkedBlockingDeque; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
        throws IllegalStateException 
    { 
  
        // create object of LinkedBlockingDeque 
        LinkedBlockingDeque<Integer> LBD 
            = new LinkedBlockingDeque<Integer>(); 
  
        // Add numbers to front of LinkedBlockingDeque 
        LBD.addFirst(7855642); 
        LBD.addFirst(35658786); 
        LBD.addFirst(5278367); 
        LBD.addFirst(74381793); 
  
        // before removing print queue 
        System.out.println("Linked Blocking Deque: " + LBD); 
  
        // prints the first element 
        System.out.println("Linked Blocking Deque first element: " +  
                                                    LBD.getFirst()); 
    } 
}

輸出：

Linked Blocking Deque: [74381793, 5278367, 35658786, 7855642]
Linked Blocking Deque first element: 74381793

示例2:

// Java Program Demonstrate getFirst() 
// method of LinkedBlockingDeque 
  
import java.util.concurrent.LinkedBlockingDeque; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
        throws IllegalStateException 
    { 
  
        // create object of LinkedBlockingDeque 
        LinkedBlockingDeque<Integer> LBD 
            = new LinkedBlockingDeque<Integer>(); 
  
        // Add numbers to front of LinkedBlockingDeque 
        LBD.addFirst(7855642); 
        LBD.addFirst(35658786); 
        LBD.addFirst(5278367); 
        LBD.addFirst(74381793) 
  
            LBD.clear(); 
  
        // Since the container is empty it will throw exception 
        System.out.println("Linked Blocking Deque first element: " +  
                                                    LBD.getFirst()); 
    } 
}

輸出：

Exception in thread "main" java.util.NoSuchElementException
    at java.util.concurrent.LinkedBlockingDeque.getFirst(LinkedBlockingDeque.java:553)
    at GFG.main(GFG.java:28)

參考： https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/LinkedBlockingDeque.html#getFirst()

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注：本文由純淨天空篩選整理自gopaldave大神的英文原創作品 LinkedBlockingDeque getFirst() method in Java。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。