public static void main(String[] args) {
		List<User> list=new ArrayList<User>();
		User user=new User();
		user.setAge(31);
		user.setName("d");
		user.setSal(8000.35);
		
		User user2=new User();
		user2.setAge(25);
		user2.setName("a");
		user2.setSal(6500.35);
		
	
		User user3=new User();
		user3.setAge(20);
		user3.setName("c");
		user3.setSal(7000.35);
		
		User user4=new User();
		user4.setAge(18);
		user4.setName("c");
		user4.setSal(3500.35);
		
		User user5=new User();
		user5.setAge(20);
		user5.setName("a");
		user5.setSal(3500.35);
		
		User user6=new User();
		user6.setAge(18);
		user6.setName("c");
		user6.setSal(1200.35);
		
		list.add(user);
		list.add(user2);
		list.add(user3);
		list.add(user4);
		list.add(user5);
		list.add(user6);
		System.out.println("----------------------------排序前-----------------------------------------");
		for(int i=0;i<list.size();i++) {
			System.out.println(list.get(i).getName()+" | "+list.get(i).getAge()+" | "+list.get(i).getSal());
		}
		
		System.out.println("----------------------------排序後-----------------------------------------");
		
		 // 排序
        Collections.sort(list, new Comparator<User>() {
            @Override
            public int compare(User o1, User o2) {
            	//按名稱排序
            	int flag=o1.getName().compareTo(o2.getName());   //這是升降，    o2.getName().compareTo(o1.getName()) ---》這是降序    （下面同理）
            	//按年齡排序
        		if(flag==0) {
        			flag=o1.getAge()-o2.getAge();
        		}
        		//按工資排序
        		if(flag==0) {
        			flag=(int)(o1.getSal()-o2.getSal());
        		}
        		return flag;
            }
        });
		

	
		for(int i=0;i<list.size();i++) {
			System.out.println(list.get(i).getName()+" | "+list.get(i).getAge()+" | "+list.get(i).getSal());
		}
	} 
 

實體類

public class User {
	 private int age; //用年齡  
	 private String name; //使用者名稱
	 private double sal;  //工資
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public double getSal() {
		return sal;
	}
	public void setSal(double sal) {
		this.sal = sal;
	}
	
}