JAVA之set系列集合

LinkedHashSet是HashSet集合的一个子类

在学习Set集合之前一定要了解一下哈希值

因此在这个时候我们需要自定义排序规则：

代码如下：

package com.sjd.Set;

import java.util.*;

public class Setcollection {
    public static void main(String[] args) {
        Set<Student> students = new TreeSet<>(new Comparator<Student>() {
            @Override
            //如果要比较小数的话，我们就需要调用Double的compare方法来进行比较了，
            //可是我写了这么多的比较方法，他会使用哪一个呢，答案是他会根据就近原则来进行调用
            public int compare(Student o1, Student o2) {
                return Double.compare(o1.getHeight(),o2.getHeight());
            }
        });
        students.add(new Student("1","小明",17,173.5));
        students.add(new Student("2","小三",18,174.5));
        students.add(new Student("3","小四",19,175.5));
        students.add(new Student("4","小五",20,176.5));
        System.out.println(students);

    }
}

package com.sjd.Set;

import java.util.Objects;

public class Student implements Comparable<Student>{
    private String no;
    private String name;
    private int  age;
    private double height;

    public Student(String no, String name, int age, double height) {
        this.no = no;
        this.name = name;
        this.age = age;
        this.height = height;
    }

    @Override
    public String toString() {
        return "Student{" +
                "no='" + no + '\'' +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", height=" + height +
                '}';
    }

    public String getNo() {
        return no;
    }

    public void setNo(String no) {
        this.no = no;
    }

    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 getHeight() {
        return height;
    }

    public void setHeight(double height) {
        this.height = height;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Student student = (Student) o;
        return age == student.age && Double.compare(student.height, height) == 0 && Objects.equals(no, student.no) && Objects.equals(name, student.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(no, name, age, height);
    }

    @Override
    public int compareTo(Student o) {
        return this.age - o.age;//这种方式是默认升序排序；
    }
}

这里需要着重提一句，如果在进行比较的过程中如果遇到比较的两个数相等的话，set集合是会去掉其中某一个数据的。