(工具)list值交換位置

package test;

import java.util.ArrayList;
import java.util.List;

public class listjiaohuan {
        public static void main(String[] args) {
            List<Integer> list=new ArrayList<Integer>();
            list.add(100);
            list.add(200);
            System.out.println("交換之前的值:"+list);
            swap(list,0,1);
            System.out.println("交換后的值:"+list);
        }
        public static void swap(List<?> list,int i,int j){
            final List l=list;
            l.set(i, l.set(j, l.get(i)));
        }
}