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());
         }
      }
 }