Java中的 BlockingDeque takeFirst() 方法及示例

BlockingDeque的takeFirst()方法返回并从中删除 Deque 容器的第一个元素，必要时等待直到元素可用。如果在等待时被中断，该方法将抛出InterruptedException 。

句法：

public E takeFirst()

返回：此方法返回 Deque 容器的第一个元素，如有必要，等待元素可用。

Exception ：如果函数在等待时被中断，则会抛出InterruptedException 。

注意： BlockingDeque的takeFirst()方法继承自Java中的 LinkedBlockingDeque 类。

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

方案一：

// 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 BD
            = new LinkedBlockingDeque();
  
        // 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 BD
            = new LinkedBlockingDeque();
  
        // 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： https: Java/util/concurrent/BlockingDeque.html#takeFirst()