实现Comparator 对List<?>进行排序

首选需要有个Entity类 ，里面有属性有方法

package demo;

public class Entity {
    private String empNo ; 
    private String empName ; 
    private float sal ; 

    public String getEmpNo() { 
    return empNo; 
    } 
    public void setEmpNo(String empNo) { 
    this.empNo = empNo; 
    } 
    public String getEmpName() { 
    return empName; 
    } 
    public void setEmpName(String empName) { 
    this.empName = empName; 
    } 
    public float getSal() { 
    return sal; 
    } 
    public void setSal(float sal) { 
    this.sal = sal; 
    } 

    public Entity(String empNo,String empName,float sal){ 
    this.empNo = empNo ; 
    this.empName = empName ; 
    this.sal = sal ; 
    } 
    
}

现在我想对 empName 这个属性进行排序

此时需要MyComparator 实现Comparator<Object>

package demo;

import java.util.Comparator;

public class MyComparator implements Comparator<Object>{ 

    public int compare(Object o1,Object o2) { 
        Entity s1 = (Entity) o1;
        Entity s2 = (Entity) o2;
//        return (int) (s1.getSal() - s2.getSal()); // 按Id排
        return s1.getEmpName().compareTo(s2.getEmpName()); // 按姓名排
    } 
} 

测试类如下

package demo;

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

public class test {
    public static void main(String[] args) {
         ArrayList<Entity> list = new ArrayList<Entity>();
        Entity e1 = new Entity(null, null, 0);
        Entity e2 = new Entity(null, null, 0);
        Entity e3 = new Entity(null, null, 0);
        Entity e4 = new Entity(null, null, 0);
        e1.setEmpName("TY2014000002");
        String s1= e1.getEmpName();
        s1 = s1.substring(6);
        System.out.println(s1+"+++++++++");
        e2.setEmpName("TY2016000009");
        e3.setEmpName("TY2016000003");
        e4.setEmpName("TY2014000001");
        list.add(e1);
        list.add(e2);
        list.add(e3);
        list.add(e4);
        for(int i=0;i<list.size();i++){ 
            Entity emp = (Entity)list.get(i) ; 
            System.out.println(emp.getEmpName()); 
        } 
        System.out.println("-------------------");
        MyComparator mc = new MyComparator() ; 
        Collections.sort(list, mc) ; 
        for(int i=0;i<list.size();i++){ 
            Entity emp = (Entity)list.get(i) ; 
            System.out.println(emp.getEmpName()); 
        }  
     }
}