Java ArrayDeque clear() 方法

描述

Java ArrayDeque clear() 方法會移除此雙端佇列中的所有元素。當我們想要重用佇列或重置佇列時，此方法非常有用。

宣告

以下是java.util.ArrayDeque.clear() 方法的宣告

public void clear()

引數

無

返回值

此方法不返回任何值。

異常

無

清除整數型 ArrayDeque 示例

以下示例演示了 Java ArrayDeque clear() 方法的使用。在這個示例中，我們使用的是 Integer。首先，我們填充 arraydeque 物件並列印它。然後我們列印 arraydeque 物件的大小並執行清除操作。清除後，我們列印 arraydeque 物件的大小，現在為 0。

package com.tutorialspoint;

import java.util.ArrayDeque;
import java.util.Deque;

public class ArrayDequeDemo {
   public static void main(String[] args) {
     
      // create an empty array deque
      Deque<Integer> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add(20);
      deque.add(30);
      deque.add(10);

      // let us print all the elements available in deque
      System.out.println("ArrayDeque = " + deque);    

      // finding size of this deque
      int retval = deque.size();
      System.out.println("Deque consists of "+ retval +" elements");

      System.out.println("Performing clear operation !!");
      deque.clear();
      retval = deque.size();
      System.out.println("Now, deque consists of "+ retval +" elements");
   }
}   

輸出

讓我們編譯並執行上述程式，這將產生以下結果：

ArrayDeque = [20, 30, 10]
Deque consists of 3 elements
Performing clear operation !!
Now, deque consists of 0 elements

清除字串型 ArrayDeque 示例

以下示例演示了 Java ArrayDeque clear() 方法的使用。在這個示例中，我們使用的是 String。首先，我們填充 arraydeque 物件並列印它。然後我們列印 arraydeque 物件的大小並執行清除操作。清除後，我們列印 arraydeque 物件的大小，現在為 0。

package com.tutorialspoint;

import java.util.ArrayDeque;
import java.util.Deque;

public class ArrayDequeDemo {
   public static void main(String[] args) {
     
      // create an empty array deque
      Deque<String> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add("A");
      deque.add("B");
      deque.add("C");

      // let us print all the elements available in deque
      System.out.println("ArrayDeque = " + deque);    

      // finding size of this deque
      int retval = deque.size();
      System.out.println("Deque consists of "+ retval +" elements");

      System.out.println("Performing clear operation !!");
      deque.clear();
      retval = deque.size();
      System.out.println("Now, deque consists of "+ retval +" elements");
   }
}   

輸出

讓我們編譯並執行上述程式，這將產生以下結果：

ArrayDeque = [A, B, C]
Deque consists of 3 elements
Performing clear operation !!
Now, deque consists of 0 elements

清除物件型 ArrayDeque 示例

以下示例演示了 Java ArrayDeque clear() 方法的使用。在這個示例中，我們使用的是 Student 物件。首先，我們填充 arraydeque 物件並列印它。然後我們列印 arraydeque 物件的大小並執行清除操作。清除後，我們列印 arraydeque 物件的大小，現在為 0。

package com.tutorialspoint;

import java.util.ArrayDeque;
import java.util.Deque;

public class ArrayDequeDemo {
   public static void main(String[] args) {
     
      // create an empty array deque
      Deque<Student> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add(new Student(1, "Julie"));
      deque.add(new Student(2, "Robert"));
      deque.add(new Student(3, "Adam"));

      // let us print all the elements available in deque
      System.out.println("ArrayDeque = " + deque);    

      // finding size of this deque
      int retval = deque.size();
      System.out.println("Deque consists of "+ retval +" elements");

      System.out.println("Performing clear operation !!");
      deque.clear();
      retval = deque.size();
      System.out.println("Now, deque consists of "+ retval +" elements");
   }
} 

class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
}  

輸出

讓我們編譯並執行上述程式，這將產生以下結果：

ArrayDeque = [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ]]
Deque consists of 3 elements
Performing clear operation !!
Now, deque consists of 0 elements