Collections 排序

blgaici1

1.Collections排序
import java.util.*;public class ArrayListTest {  public static void printElements(Collection c){  Iterator it=c.iterator();  while(it.hasNext()){    System.out.println(it.next());      } } public static void main(String[] args){  ArrayList a1=new ArrayList();  Student s1=new Student(4,"zhangsan");  Student s2=new Student(2,"lisi");  Student s3=new Student(3,"wangwu");  Student s4=new Student(4,"mybole");    a1.add(s1);  a1.add(s2);  a1.add(s3);  a1.add(s4);  Collections.sort(a1);//  Collections.sort(a1,new Student.StudentComparator());  printElements(a1);  System.out.println(Collections.max(a1));     }}class Point{ int x, y; Point(int x,int y){  this.x=x;  this.y=y; } public String toString(){  return ("x="+x+","+"y="+y); }}class Student implements Comparable{ int num; String name; Student(int num,String name){  this.num=num;  this.name=name; }  static class StudentComparator implements Comparator{  public int compare(Object o1,Object o2){   Student s1=(Student) o1;   Student s2=(Student) o2;   int result=s1.num>s2.num?1:(s1.num==s2.num?0:-1);   if (result==0){    result=s1.name.compareTo(s2.name);   }   return result;   } }  public int compareTo(Object arg0) {  Student s=(Student) arg0;  return num>s.num?1:(num==s.num?0:-1); }   public String toString(){ return "num:"+num+","+"name:"+name; }}