Java.util.ArrayList.clear()方法範例

java.util.ArrayList.clear() 方法移除此列表中的元素。該列表為空後，這個呼叫返回。

宣告

以下是java.util.ArrayList.clear()方法的宣告

public void clear()

引數

• NA

返回值

此方法不返回任何值。

異常

• NA

例子

下面的範例演示java.util.Arraylist.clear()方法的用法。

package com.yiibai;

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");
   }
}   

讓我們來編譯和執行上面的程式，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