Java BlockingDeque takeFirst()方法及示例

BlockingDeque 的 takeFirst() 方法返回并删除Deque容器中的第一个元素，如果有必要，可以等待，直到有元素可用。如果在等待过程中被打断，该方法会抛出一个InterruptedException。

语法

public E takeFirst()

返回： 该方法返回Deque容器的第一个元素，如果有必要，可以等待，直到有元素可用。

异常 ：如果在等待时被打断，该函数会抛出一个InterruptedException。

注意 ： BlockingDeque 的 takeFirst() 方法是从Java的LinkedBlockingDeque类中继承的。

下面的程序说明了LinkedBlockingDeque的takeFirst()方法。

程序1 :

// Java Program to demonstrate takeFirst()
// method of BlockingDeque
  
import java.util.concurrent.BlockingDeque;
import java.util.concurrent.BlockingDeque;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
        throws InterruptedException
    {
  
        // create object of BlockingDeque
        BlockingDeque<Integer> BD
            = new LinkedBlockingDeque<Integer>();
  
        // Add numbers to end of BlockingDeque
        BD.add(7855642);
        BD.add(35658786);
        BD.add(5278367);
        BD.add(74381793);
  
        // print Deque
        System.out.println("Blocking Deque: " + BD);
  
        // removes the front element and prints it
        System.out.println("Head of Blocking Deque: "
                           + BD.takeFirst());
  
        // prints the Deque
        System.out.println("Blocking Deque: " + BD);
    }
}

输出:

Blocking Deque: [7855642, 35658786, 5278367, 74381793]
Head of Linked Deque: 7855642
Blocking Deque: [35658786, 5278367, 74381793]

程序2： 演示InterruptedException

// Java Program to demonstrate takeFirst()
// method of BlockingDeque
  
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.BlockingDeque;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
        throws InterruptedException
    {
  
        // create object of BlockingDeque
        BlockingDeque<Integer> BD
            = new LinkedBlockingDeque<Integer>();
  
        // Add numbers to end of BlockingDeque
        BD.add(7855642);
        BD.add(35658786);
        BD.add(5278367);
        BD.add(74381793);
  
        // print Dequeue
        System.out.println("Blocking Deque: " + BD);
  
        BD.clear();
  
        // throws error as the list is empty and it
        // is interrupted while waiting
        System.out.println("Head of Blocking Deque: "
                           + BD.takeFirst());
    }
}

运行时错误

Max real time limit exceeded due to either by heavy load on server or by using sleep function

**参考资料: **https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/BlockingDeque.html#takeFirst()