首选需要有个Entity类 ，里面有属性有方法
1 package demo;
2
3 public class Entity {
4 private String empNo ;
5 private String empName ;
6 private float sal ;
7
8 public String getEmpNo() {
9 return empNo;
10 }
11 public void setEmpNo(String empNo) {
12 this.empNo = empNo;
13 }
14 public String getEmpName() {
15 return empName;
16 }
17 public void setEmpName(String empName) {
18 this.empName = empName;
19 }
20 public float getSal() {
21 return sal;
22 }
23 public void setSal(float sal) {
24 this.sal = sal;
25 }
26
27 public Entity(String empNo,String empName,float sal){
28 this.empNo = empNo ;
29 this.empName = empName ;
30 this.sal = sal ;
31 }
32
33 }
现在我想对 empName 这个属性进行排序
此时需要MyComparator 实现Comparator<Object>
1 package demo;
2
3 import java.util.Comparator;
4
5 public class MyComparator implements Comparator<Object>{
6
7 public int compare(Object o1,Object o2) {
8 Entity s1 = (Entity) o1;
9 Entity s2 = (Entity) o2;
10 // return (int) (s1.getSal() - s2.getSal()); // 按Id排
11 return s1.getEmpName().compareTo(s2.getEmpName()); // 按姓名排
12 }
13 }
测试类如下
1 package demo;
2
3 import java.util.ArrayList;
4 import java.util.Collections;
5
6 public class test {
7 public static void main(String[] args) {
8 ArrayList<Entity> list = new ArrayList<Entity>();
9 Entity e1 = new Entity(null, null, 0);
10 Entity e2 = new Entity(null, null, 0);
11 Entity e3 = new Entity(null, null, 0);
12 Entity e4 = new Entity(null, null, 0);
13 e1.setEmpName("TY2014000002");
14 String s1= e1.getEmpName();
15 s1 = s1.substring(6);
16 System.out.println(s1+"+++++++++");
17 e2.setEmpName("TY2016000009");
18 e3.setEmpName("TY2016000003");
19 e4.setEmpName("TY2014000001");
20 list.add(e1);
21 list.add(e2);
22 list.add(e3);
23 list.add(e4);
24 for(int i=0;i<list.size();i++){
25 Entity emp = (Entity)list.get(i) ;
26 System.out.println(emp.getEmpName());
27 }
28 System.out.println("-------------------");
29 MyComparator mc = new MyComparator() ;
30 Collections.sort(list, mc) ;
31 for(int i=0;i<list.size();i++){
32 Entity emp = (Entity)list.get(i) ;
33 System.out.println(emp.getEmpName());
34 }
35 }
36 }
