JAVA中Comparable接口和自定义比较器示例讲解

自然排序

TreeSet集合在存储数据时有一定的顺序，它会将一些数据进行比较，比较调用的是comparaTo（）方法，该方法是在Comparable中定义的，自然排序要求TreeSet集合中存储的数据必须实现Comparable接口，并且重写ComparaTo（）方法

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;
}
}

运行结果

[Teacher{name='Jack', age=19}, Teacher{name='Tom', age=19}, Teacher{name='King', age=20}, Teacher{name='Rose', age=20}]

定制排序

如果单单使用ComparaTo（）不能满足要求，这时可以通过在创建TreeSet集合的时候就自定义一个比较器来对元素进行定制排序

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;
}
}

结果

[Tom, Jack, Helena]

来源：https://blog.csdn.net/heiren_a/article/details/109006057