Java 中的 BlockingDeque putFirst()方法，带示例

原文:https://www . geeksforgeeks . org/blocking eque-put first-method-in-Java-with-examples/

阻塞请求的 putFirst(E e) 方法将指定的元素插入到这个命令所代表的队列的前面。如果德奎是容量受限的，那么它将等待空间变得可用。

语法:

public void putFirst(E e)

参数:该方法接受一个强制参数 e ，它是要插入到阻塞请求前面的元素。

返回:此方法不返回任何内容。

异常:程序抛出如下所示的两个异常:

  • null pointerexception -If the specified element is empty
  • Interrupt exception –If you interrupt while waiting

注:blocking eque的 putFirst()方法继承自 Java 中的link edblocking eque类。

下面的程序说明了 putFirst()方法的阻塞请求:

程序 1:

// Java Program Demonstrate putFirst()
// 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.putFirst(7855642);
        BD.putFirst(35658786);
        BD.putFirst(5278367);
        BD.putFirst(74381793);

        // print Deque
        System.out.println("Blocking Deque: " + BD);
    }
}

输出:

Blocking Deque: [74381793, 5278367, 35658786, 7855642]

节目 2:

// Java Program Demonstrate putFirst()
// method of BlockingDeque
// throwing NullPointerException

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.putFirst(7855642);
        BD.putFirst(35658786);
        BD.putFirst(5278367);

        // throws an exception
        BD.putFirst(null);

        // print Dequeue
        System.out.println("Blocking Deque: " + BD);
    }
}

输出 :

Exception in thread "main" java.lang.NullPointerException
    at java.util.concurrent.LinkedBlockingDeque.putFirst(LinkedBlockingDeque.java:373)
    at GFG.main(GFG.java:24)

节目 3:

// Java Program Demonstrate putFirst()
// method of BlockingDeque
// when capacity exceeded

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>(3);

        // Add numbers to end of BlockingDeque
        BD.putFirst(7855642);
        BD.putFirst(35658786);
        BD.putFirst(5278367);

        // throws an exception
        BD.putFirst(4356789);

        // print Dequeue
        System.out.println("Blocking Deque: " + BD);
    }
}

输出 :

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

参考:T2【https://docs . Oracle . com/javase/7/docs/API/Java/util/concurrent/blockingdequee . html # putFirst(E)

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