java Java 中的 linkedblockingrequegetfirst()方法

Java 中的 linkedblockingrequegetfirst()方法

原文:https://www . geeksforgeeks . org/linkedblockingreque-get first-method-in-Java/

的 getFirst() 方法 link edblockingrequest返回 Deque 容器中最前面的元素。如果 LinkedBlockingDeque 为空，那么在函数调用时，它会返回一个 NoSuchElementException 。

语法:

public E getLast()

参数:此方法不接受任何参数。

返回:这个方法返回第一个元素或者这个 Deque 容器的头。

异常:该函数在 deque 为空时只抛出一个异常，即no suchelementexception

下面的程序说明了链接锁定请求的 getFirst()方法:

程序 1:

// Java Program Demonstrate getFirst()
// method of LinkedBlockingDeque

import java.util.concurrent.LinkedBlockingDeque;
import java.util.*;

public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {

        // create object of LinkedBlockingDeque
        LinkedBlockingDeque<Integer> LBD
            = new LinkedBlockingDeque<Integer>();

        // Add numbers to front of LinkedBlockingDeque
        LBD.addFirst(7855642);
        LBD.addFirst(35658786);
        LBD.addFirst(5278367);
        LBD.addFirst(74381793);

        // before removing print queue
        System.out.println("Linked Blocking Deque: " + LBD);

        // prints the first element
        System.out.println("Linked Blocking Deque first element: " + 
                                                    LBD.getFirst());
    }
}

输出:

Linked Blocking Deque: [74381793, 5278367, 35658786, 7855642]
Linked Blocking Deque first element: 74381793

节目 2:

// Java Program Demonstrate getFirst()
// method of LinkedBlockingDeque

import java.util.concurrent.LinkedBlockingDeque;
import java.util.*;

public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {

        // create object of LinkedBlockingDeque
        LinkedBlockingDeque<Integer> LBD
            = new LinkedBlockingDeque<Integer>();

        // Add numbers to front of LinkedBlockingDeque
        LBD.addFirst(7855642);
        LBD.addFirst(35658786);
        LBD.addFirst(5278367);
        LBD.addFirst(74381793)

            LBD.clear();

        // Since the container is empty it will throw exception
        System.out.println("Linked Blocking Deque first element: " + 
                                                    LBD.getFirst());
    }
}

输出:

Exception in thread "main" java.util.NoSuchElementException
    at java.util.concurrent.LinkedBlockingDeque.getFirst(LinkedBlockingDeque.java:553)
    at GFG.main(GFG.java:28)