Java中的 BlockingDeque putFirst() 方法及示例

BlockingDeque的putFirst(E e)方法将指定元素插入到此双端队列表示的队列的前面。如果双端队列容量受限，那么它将等待空间可用。

句法：

public void putFirst(E e)

参数：此方法接受一个强制参数e ，它是要插入到 BlockingDeque 前面的元素。

返回：此方法不返回任何内容。

异常：程序抛出两个异常，如下所示：

• NullPointerException – 如果指定元素为 null
• InterruptedException – 如果在等待时被中断

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

下面的程序说明了 BlockingDeque 的 putFirst() 方法：

方案一：

// 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 BD
            = new LinkedBlockingDeque();
  
        // 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]

方案二：

// 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 BD
            = new LinkedBlockingDeque();
  
        // 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)

方案 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 BD
            = new LinkedBlockingDeque(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： https: Java/util/concurrent/BlockingDeque.html#putFirst(E)