Collections-sort

import java.util.ArrayList;

 import java.util.Collections;

 import java.util.List;

 /*

  * 1.Collections.sort(list);只能对List排序，注意：list中的
 * 元素类型必须具备可比较性(继承Comparable)
     2.Collections.sort(list,new StrLenComparator());//指定比较器升序
  */

 public class CollectionsTest {

 public static void main(String[] args) {

sortDemo();

 }

 public static void sortDemo(){

List<String>  list=new ArrayList<String>();

list.add("aasd");

list.add("aaa");

list.add("aaa");

list.add("dd");

list.add("ss");

list.add("gg");

System.out.println(list.toString());

Collections.sort(list);//默认升序

System.out.println(list.toString());


Collections.sort(list,new StrLenComparator());//指定比较器升序

System.out.println(list.toString());

 }


}
//**************************************************************
import java.util.Comparator;


 public class StrLenComparator implements Comparator<String>{


@Override
public int compare(String s1, String s2) {
// TODO Auto-generated method stub
if(s1.length()>s2.length()){
return 1;
}
if(s1.length()<s2.length()){
return -1;
}

return s1.compareTo(s2);
}


 }