Java 集合 ArrayList set()方法

package beginnersbook.com;
import java.util.ArrayList;
public class SetExample {
  public static void main(String args[]) {
    ArrayList<Integer> arraylist = new ArrayList<Integer>();
    arraylist.add(1);
    arraylist.add(2);
    arraylist.add(3);
    arraylist.add(4);
    arraylist.add(5);
    arraylist.add(6);
    arraylist.add(7);
    System.out.println("ArrayList before update: "+arraylist);
    //Updating 1st element
    arraylist.set(0, 11);
    //Updating 2nd element
    arraylist.set(1, 22);
    //Updating 3rd element
    arraylist.set(2, 33);
    //Updating 4th element
    arraylist.set(3, 44);
    //Updating 5th element
    arraylist.set(4, 55);
    System.out.println("ArrayList after Update: "+arraylist);
  }
}

ArrayList before update: [1, 2, 3, 4, 5, 6, 7]
ArrayList after Update: [11, 22, 33, 44, 55, 6, 7]