comparable接口和comparator接口有什么区别和联系啊？ - 黑马程序员技术交流社区

package com.itheima;
import java.util.Iterator;
import java.util.TreeSet;
public class Test10 {
public static void main(String[] args) {
//声明创建TreeSet集合泛型为Student
TreeSet<Student> set = new TreeSet<Student>();
//声明创建五个student并加入set集合
Student stu1 = new Student("小明", 23, 98.5);
Student stu2 = new Student("小红", 24, 45.6);
Student stu3 = new Student("小强", 25, 84.2);
Student stu4 = new Student("小刚", 26, 84.2);
Student stu5 = new Student("小松", 23, 98);
set.add(stu1);
set.add(stu2);
set.add(stu3);
set.add(stu4);
set.add(stu5);
System.out.println("set大小:" + set.size());
//调用所定义的对set集合的输出函数
Myout(set);
}
public static void Myout(TreeSet<Student> set) {
//迭代set集合
Iterator<Student> it = set.iterator();
//取出迭代器中的元素
while (it.hasNext()) {
Student stu = (Student) it.next();
System.out.println(stu.toString());
}
}
}
/*
* 定义Student类，并继承Comparable并实现compareto()方法
* 在此我直接将泛型加入，省去compareto()中的强转
*
*/
class Student implements Comparable<Student>{
private String name;
private int age;
private double score;
public Student() {
}
//增加带参数构造器方便添加数据
public Student(String name, int age, double score) {
super();
this.name = name;
this.age = age;
this.score = score;
}
//增加get set 方法
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public double getScore() {
return score;
}
public void setScore(double score) {
this.score = score;
}
//覆盖compareTo()方法，定义出自己所需的情况
@Override
public int compareTo(Student o) {
Student stu = o;
//下面几个if else 语句实现了先通过分数进行排序和年龄进行排序
//如果两者都相同则通过姓名进行排序。
//返回的-1、1和0也可以是其它的证书或者负数
if (this.score < stu.score)
return (int) -1;
else if (this.score > stu.score)
return 1;
else if (this.age > stu.age)
return 1;
else if (this.age < stu.age)
return -1;
else if (this.score == stu.score && this.age == stu.age)
//分数年龄相同则返回姓名的字典顺序差。
return this.name.compareTo(stu.name);
return 0;
}
//覆盖toString()方法方便调试和显示
@Override
public String toString() {
return "Student [age=" + age + ", name=" + name + ", score=" + score
+ "]";
}
}

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package com.itheima;
import java.util.Comparator;
import java.util.Iterator;
import java.util.TreeSet;
public class Test10 {
/**
* 10、声明类Student，包含3个成员变量：name、age、score，创建5个对象装入TreeSet，
* 按照成绩排序输出结果（考虑成绩相同的问题）。
*/
public static void main(String[] args) {
//声明创建TreeSet集合泛型为Student
TreeSet<Student> set = new TreeSet<Student>(new myStudentComparactor());
//声明创建五个student并加入set集合
Student stu1 = new Student("小明", 23, 98.5);
Student stu2 = new Student("小红", 24, 45.6);
Student stu3 = new Student("小强", 25, 84.2);
Student stu4 = new Student("小刚", 26, 84.2);
Student stu5 = new Student("小松", 23, 98);
set.add(stu1);
set.add(stu2);
set.add(stu3);
set.add(stu4);
set.add(stu5);
System.out.println("set大小:" + set.size());
//调用所定义的对set集合的输出函数
Myout(set);
}
public static void Myout(TreeSet<Student> set) {
//迭代set集合
Iterator<Student> it = set.iterator();
//取出迭代器中的元素
while (it.hasNext()) {
Student stu = (Student) it.next();
System.out.println(stu.toString());
}
}
}
class Student {
private String name;
private int age;
private double score;
public Student() {
}
//增加带参数构造器方便添加数据
public Student(String name, int age, double score) {
super();
this.name = name;
this.age = age;
this.score = score;
}
//增加get set 方法
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public double getScore() {
return score;
}
public void setScore(double score) {
this.score = score;
}
//覆盖toString()方法方便调试和显示
@Override
public String toString() {
return "Student [age=" + age + ", name=" + name + ", score=" + score
+ "]";
}
}
//自定义排序器
class myStudentComparactor implements Comparator<Student>{
@Override
public int compare(Student o1, Student o2) {
if (o1.getScore() > o2.getScore())
return (int) -1;
else if (o1.getScore() < o2.getScore())
return 1;
else if (o1.getAge() > o2.getAge())
return 1;
else if (o1.getAge() < o2.getAge())
return -1;
else if (o1.getScore() == o2.getScore() && o1.getAge() == o2.getAge())
return o1.getName().compareTo(o2.getName());
return 0;
}
}

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