Java BlockingDeque putFirst()方法及示例

BlockingDeque 的 putFirst(E e) 方法将指定的元素插入到这个deque所代表的队列的前面。如果Deque有容量限制，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BlockingDeque前面的元素。

返回： 该方法不返回任何东西。

异常： 该程序抛出两个异常，如下所示。

• NullPointerException – 如果指定的元素是空的。
• InterruptedException – 如果在等待时被打断。

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

下面的程序说明了BlockingDeque的putFirst()方法。

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]

程序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)

程序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

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