Java LinkedBlockingDeque getFirst()用法及代码示例

LinkedBlockingDeque的getFirst()方法返回Deque容器中最前面的元素。如果LinkedBlockingDeque为空，则在函数调用时将返回NoSuchElementException。

用法:

public E getLast()

参数：此方法不接受任何参数。

返回值：此方法返回此Deque容器的第一个元素或头。

异常：当双端队列为空时，该函数仅引发一个异常，即NoSuchElementException

以下示例程序旨在说明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()); 
    } 
}

输出：

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()); 
    } 
}

输出：

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

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

相关用法

注：本文由纯净天空筛选整理自gopaldave大神的英文原创作品 LinkedBlockingDeque getFirst() method in Java。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。