与c++中的qsort的实现极为相似，构建新的比较对象Comparator即可

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;

class Student{
	public int age;
	private String name;
	public Student(String name,int age){
		this.age=age;
		this.name=name;
	}
	public String toString(){
		String str=name+"is "+age;
		return str;
	}
}
public class Sort{
	public static void main(String[] args){
		ArrayList<Student> s=new ArrayList<Student>();
		s.add(new Student("cjc",25));
		s.add(new Student("jake",17));
		s.add(new Student("john",30));
		s.add(new Student("Alice",23));
			
		System.out.println("The order before sorting!");
		System.out.println(s);
		
		//对集合中的元素更具年龄进行排序
		Collections.sort(s,new Comparator(){
			@Override
			public int compare(Object o1, Object o2) {
				// TODO Auto-generated method stub
				Student stu1=(Student)o1;
				Student stu2=(Student)o2;
				return stu2.age-stu1.age;
			}
		});
		System.out.println("The order after sorting!");
		System.out.println(s);
		
	}
}

java ArrayList根据存储对象排序