JAVA中Comparable接口和自定义比较器示例讲解

public class 自然排序 {
 public static void main(String[] args) {
 //定义一个TreeSet集合
 TreeSet treeSet = new TreeSet();
 Teacher t1 = new Teacher("Jack",19);
 Teacher t2 = new Teacher("King",20);
 Teacher t3 = new Teacher("Tom",19);
 Teacher t4 = new Teacher("Rose",20);
 treeSet.add(t1);
 treeSet.add(t2);
 treeSet.add(t3);
 treeSet.add(t4);
 System.out.println(treeSet);
 }
}
//定义Teacher类实现Comparable接口
class Teacher implements Comparable{

 String name;
 int age;
 public Teacher(String name,int age){
 this.name = name;
 this.age = age;
 }
 //重写toString方法
 @Override
 public String toString() {
 return "Teacher{" +
  "name='" + name + '\'' +
  ", age=" + age +
  '}';
 }
 //先比较年龄在比较名字
 @Override
 public int compareTo(Object o) {
 Teacher teacher = (Teacher)o;
 if (this.age > teacher.age){
  return 1;
 }
 if (this.age == teacher.age){
  return this.name.compareTo(teacher.name);
 }
 return -1;
 }
}

import java.util.Comparator;
import java.util.TreeSet;

public class 定制排序 {
 public static void main(String[] args) {
 //在创建集合是传入比较器
 TreeSet treeSet = new TreeSet(new MyComparable());
 treeSet.add("Jack");
 treeSet.add("Tom");
 treeSet.add("Helena");
 System.out.println(treeSet);
 }
}
//自定义的比较器
class MyComparable implements Comparator{

 @Override
 public int compare(Object o1, Object o2) {
 //以单词的长度来排序
 String s1 = (String)o1;
 String s2 = (String)o2;
 int resoult = s1.length() - s2.length();
 return resoult;
 }
}