Java Queue remove()方法

Queue接口 的 remove() 方法返回并删除容器前端的元素。它删除了容器的头部。当队列为空时，该方法会抛出一个 NoSuchElementException 。

语法

E remove()

返回： 该方法返回队列的 头部 。

异常： 当队列为空时，该函数抛出一个NoSuchElementException。

下面的程序说明了queue的remove()方法。

程序1： 在 LinkedList 的帮助下 。

// Java Program Demonstrate remove()
// method of Queue
 
import java.util.*;
 
public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {
 
        // create object of Queue
        Queue<Integer> Q
            = new LinkedList<Integer>();
 
        // Add numbers to end of Queue
        Q.add(7855642);
        Q.add(35658786);
        Q.add(5278367);
        Q.add(74381793);
 
        // print queue
        System.out.println("Queue: " + Q);
 
        // print head and deletes the head
        System.out.println("Queue's head: " + Q.remove());
 
        // print head and deleted the head
        System.out.println("Queue's head: " + Q.remove());
    }
}

输出

Queue: [7855642, 35658786, 5278367, 74381793]
Queue's head: 7855642
Queue's head: 35658786

程序2： 在 ArrayDeque 的帮助下 。

// Java Program Demonstrate remove()
// method of Queue
 
import java.util.*;
 
public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {
 
        // create object of Queue
        Queue<Integer> Q
            = new ArrayDeque<Integer>();
 
        // Add numbers to end of Queue
        Q.add(7855642);
        Q.add(35658786);
        Q.add(5278367);
        Q.add(74381793);
 
        // print queue
        System.out.println("Queue: " + Q);
 
        // print head and deletes the head
        System.out.println("Queue's head: " + Q.remove());
 
        // print head and deleted the head
        System.out.println("Queue's head: " + Q.remove());
    }
}

输出

Queue: [7855642, 35658786, 5278367, 74381793]
Queue's head: 7855642
Queue's head: 35658786

程序3： 在 LinkedBlockingDeque 的帮助下 。

// Java Program Demonstrate remove()
// method of Queue
 
import java.util.*;
import java.util.concurrent.LinkedBlockingDeque;
 
public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {
 
        // create object of Queue
        Queue<Integer> Q
            = new LinkedBlockingDeque<Integer>();
 
        // Add numbers to end of Queue
        Q.add(7855642);
        Q.add(35658786);
        Q.add(5278367);
        Q.add(74381793);
 
        // print queue
        System.out.println("Queue: " + Q);
 
        // print head and deletes the head
        System.out.println("Queue's head: " + Q.remove());
 
        // print head and deleted the head
        System.out.println("Queue's head: " + Q.remove());
    }
}

输出

Queue: [7855642, 35658786, 5278367, 74381793]
Queue's head: 7855642
Queue's head: 35658786

程序4： 在 ConcurrentLinkedDeque 的帮助下 。

// Java Program Demonstrate remove()
// method of Queue
 
import java.util.*;
import java.util.concurrent.ConcurrentLinkedDeque;
 
public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {
 
        // create object of Queue
        Queue<Integer> Q
            = new ConcurrentLinkedDeque<Integer>();
 
        // Add numbers to end of Queue
        Q.add(7855642);
        Q.add(35658786);
        Q.add(5278367);
        Q.add(74381793);
 
        // print queue
        System.out.println("Queue: " + Q);
 
        // print head and deletes the head
        System.out.println("Queue's head: " + Q.remove());
 
        // print head and deleted the head
        System.out.println("Queue's head: " + Q.remove());
    }
}

输出

Queue: [7855642, 35658786, 5278367, 74381793]
Queue's head: 7855642
Queue's head: 35658786

下面的程序说明了 这个方法抛出的异常 ：

程序5： 显示 NoSuchElementException

// Java Program Demonstrate remove()
// method of Queue
 
import java.util.*;
 
public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {
 
        // create object of Queue
        Queue<Integer> Q
            = new LinkedList<Integer>();
 
        // Add numbers to end of Queue
        Q.add(423);
        Q.add(3432);
 
        // print queue
        System.out.println("Queue: " + Q);
 
        // print head and deletes the head
        System.out.println("Queue's head: " + Q.remove());
 
        // print head and deleted the head
        System.out.println("Queue's head: " + Q.remove());
 
        // print queue
        System.out.println("Queue: " + Q);
 
        try {
            // Queue is empty now hence exception
            System.out.println("Queue's head: " + Q.element());
        }
        catch (Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}

输出

Queue: [423, 3432]
Queue's head: 423
Queue's head: 3432
Queue: []
Exception: java.util.NoSuchElementException

参考资料: https://docs.oracle.com/javase/8/docs/api/java/util/Queue.html#remove-