package com.sxt.set5;

public class Student{

    private String name;

    private int age;

    private double salary;

    public Student(String name, int age, double salary) {

        super();

        this.name = name;

        this.age = age;

        this.salary = salary;

    }

    public Student() {

        super();

    }

    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 getSalary() {

        return salary;

    }

    public void setSalary(double salary) {

        this.salary = salary;

    }

    @Override

    public String toString() {

        return "Student [name=" + name + ", age=" + age + ", salary=" + salary + "]";

    }

    @Override

    public boolean equals(Object obj) {

        if (this == obj)

            return true;

        if (obj == null)

            return false;

        if (getClass() != obj.getClass())

            return false;

        Student other = (Student) obj;

        if (age != other.age)

            return false;

        if (name == null) {

            if (other.name != null)

                return false;

        } else if (!name.equals(other.name))

            return false;

        if (Double.doubleToLongBits(salary) != Double.doubleToLongBits(other.salary))

            return false;

        return true;

    }

}

package com.sxt.set5;

import java.util.Comparator;

/*

 * TreeSet：有序

 * implements Comparator<Student>

 * 如果用外部比较器TreeSet必须是实现Comparator接口来实现有序

 * 使用泛型是为了在重写compare()方法时，object不用强制转换类型

 */

//外部比较器：在新建类内重写比较规则即compare()方法

public class SalarySortOfStudent implements Comparator<Student>{

    //外部比较器的自定义比较规则：按照salary排序

    @Override

    public int compare(Student o1, Student o2) {

        //double类型的比较：不能直接写成return o1.getSalary-o2.getSalary

        //因为方法重写 返回值类型为基本数据类型必须一致  所以返回double会转成int会损失精度

        if(o1.getSalary() < o2.getSalary()){//降序

            return 1;

        }else{

            return -1;//不能是0即不能返回相等 否则结果会少输出 因为Set接口是（无序，唯一）

        }

    }

}

package com.sxt.set5;

import java.util.Comparator;

/*

 * 外部比较器：名字相同时 按照年龄降序输出

 * 实现Comparator  重写比较规则即compare()方法

 */

public class NameSortOfStudent implements Comparator<Student>{

    @Override

    public int compare(Student stu1, Student stu2) {

        if(stu1.getName().equals(stu2.getName())){

            return stu2.getAge() - stu1.getAge();

        }

        return stu1.getName().compareTo(stu2.getName());

        //String类已经实现了Comparable接口 已经重写了compareTo()方法

    }

}

package com.sxt.set5;

import java.util.HashSet;

/*

 * TreeSet 有序的 二叉树（红黑数）

 */

import java.util.Set;

import java.util.TreeSet;

public class TestStudent {

    public static void main(String[] args) {

        //排序之比较规则

        SalarySortOfStudent ss = new SalarySortOfStudent();

        TreeSet<Student> arr = new TreeSet<>(ss);//ss:外部比较器即比较规则

        arr.add(new Student("bbb", 21, 532.2));

        arr.add(new Student("ccc", 32, 32.2));

        arr.add(new Student("ddd", 11, 352.2));

        arr.add(new Student("aaa", 15, 32.2));

        //遍历

        System.out.println("按照外部比较器按薪资降序排列:");

        for(Student s:arr){

            System.out.println(s);

        }

//        按照外部比较器按薪资（double）降序排列 结果为：

//        Student [name=bbb, age=21, salary=532.2]

//        Student [name=ddd, age=11, salary=352.2]

//        Student [name=aaa, age=15, salary=32.2]

//        Student [name=ccc, age=32, salary=32.2]

        System.out.println("----------------------------------------");

        NameSortOfStudent ns = new NameSortOfStudent();

        TreeSet<Student> arr1 = new TreeSet<>(ns);//ns:外部比较器即比较规则

        arr1.add(new Student("bbb", 21, 532.2));

        arr1.add(new Student("ccc", 32, 32.2));

        arr1.add(new Student("aaa", 11, 352.2));

        arr1.add(new Student("aaa", 15, 32.2));

        System.out.println("按照外部比较器按名字排序（如果名字相同则按年龄降序排序）:");

        for(Student s:arr1){

            System.out.println(s);

        }

//        按照外部比较器按名字排序（如果名字相同则按年龄降序排序）:

//        Student [name=aaa, age=15, salary=32.2]

//        Student [name=aaa, age=11, salary=352.2]

//        Student [name=bbb, age=21, salary=532.2]

//        Student [name=ccc, age=32, salary=32.2]

    }

}