Java ArrayList ensureCapacity方法

package com.codingdict;

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
      arrlist.add(10);
      arrlist.add(50);
      arrlist.add(30);

      // this will increase the capacity of the ArrayList to 15 elements
      arrlist.ensureCapacity(15);

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