list集合的排序Comparator和Collections.sort

一个例子

package sortt;

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

public class HomeWork {

    public static void main(String[] args) {
        List<Emp> ems =new ArrayList<Emp>();
        ems.add(new Emp("Terry", 25, ‘m‘, 6000));
        ems.add(new Emp("Allen", 21, ‘f‘, 4000));
        ems.add(new Emp("Smith", 23, ‘m‘, 3000));
        System.out.println(ems);         //[(Terry,25,m,6000.0), (Allen,21,f,4000.0), (Smith,23,m,3000.0)]
        Comparator<Emp> com=new Comparator<Emp>(){ //匿名内部类

            public int compare(Emp o1, Emp o2) {
                // TODO Auto-generated method stub
                return (int) (o1.getSalary()-o2.getSalary());
            }
        };
        Collections.sort(ems,com);
        System.out.println(ems);           //[(Smith,23,m,3000.0), (Allen,21,f,4000.0), (Terry,25,m,6000.0)]

    }

}

Emp.java

class Emp{
    private String name;
    private int age;
    private char gender;
    private double salary;
    public Emp(String name, int age, char gender, double salary) {
        super();
        this.name = name;
        this.age = age;
        this.gender = gender;
        this.salary = salary;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public char getGender() {
        return gender;
    }
    public void setGender(char gender) {
        this.gender = gender;
    }
    public double getSalary() {
        return salary;
    }
    public void setSalary(double salary) {
        this.salary = salary;
    }
    public String toString(){
        return "("+name+","+  age+"," +gender+"," + salary+")";

    }

}