Java Java.util.ArrayList.clear()用法及代碼示例

描述

這個java.util.ArrayList.clear()方法從此列表中刪除所有元素。此調用返回後，列表將為空。

聲明

以下是聲明java.util.ArrayList.clear()方法

public void clear()

參數

NA

返回值

此方法不返回任何值。

異常

NA

示例

下麵的例子展示了 java.util.Arraylist.clear() 方法的用法。

package com.tutorialspoint;

import java.util.ArrayList;

public class ArrayListDemo {
   public static void main(String[] args) {
     
      // create an empty array list with an initial capacity
      ArrayList<Integer> arrlist = new ArrayList<Integer>(5);

      // use add() method to add elements in the list
      arrlist.add(20);
      arrlist.add(30);
      arrlist.add(10);
      arrlist.add(50);

      // let us print all the elements available in list
      for (Integer number:arrlist) {
         System.out.println("Number = " + number);
      }      

      // finding size of this list
      int retval = arrlist.size();
      System.out.println("List consists of "+ retval +" elements");
         
      System.out.println("Performing clear operation !!");
      arrlist.clear();
      retval = arrlist.size();
      System.out.println("Now, list consists of "+ retval +" elements");
   }
}

讓我們編譯並運行上麵的程序，這將產生以下結果——

Number = 20
Number = 30
Number = 10
Number = 50
List consists of 4 elements
Performing clear operation !!
Now, list consists of 0 elements