Java Queue remove()用法及代碼示例

隊列接口的remove()方法返回並移除容器前麵的元素。刪除容器的頭部。隊列為空時，此方法將引發NoSuchElementException。

用法:

E remove()

返回值：此方法返回隊列的頭部。

異常：隊列為空時，該函數將引發NoSuchElementException。

以下示例程序旨在說明隊列的remove()方法：

示例1:借助LinkedList。

// 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()); 
    } 
}

輸出：

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

示例2:借助ArrayDeque。

// 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()); 
    } 
}

輸出：

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

示例3:借助LinkedBlockingDeque。

// 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()); 
    } 
}

輸出：

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

示例4:借助ConcurrentLinkedDeque。

// 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()); 
    } 
}

輸出：

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

以下示例程序旨在說明此方法引發的異常：

示例5:顯示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); 
        } 
    } 
}

輸出：

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

參考： https://docs.oracle.com/javase/8/docs/api/java/util/Queue.html#remove–

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