集合应用，展示学生信息

1.创建学生类

package Java0910;

import java.util.Objects;

public class Student {
    
    String name;
    int age;
    String phone;

    public Student(String name, int age, String phone) {
    
        this.name = name;
        this.age = age;
        this.phone = phone;
    }

    @Override
    public String toString() {
    
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", phone='" + phone + '\'' +
                '}';
    }

    @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 && Objects.equals(name, student.name) && Objects.equals(phone, student.phone);
    }

    @Override
    public int hashCode() {
    
        return Objects.hash(name, age, phone);
    }
}

package Java0910;

import java.util.ArrayList;
import java.util.List;

public class List02 {
    
    public static void main(String[] args) {
    
        Student s = new Student("晓晓", 20, "15373412345");
        Student s1 = new Student("小小", 21, "132479069");

        List l = new ArrayList();
        l.add(s);
        l.add(s1);

        for (Object e : l) {
    
            System.out.println(e);
        }
    }
}

2.用Map封装学生信息

package Java0910;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class List02 {
    
    public static void main(String[] args) {
    
        Map m = new HashMap();
        m.put("name", "晓晓");
        m.put("age", 20);
        m.put("phone", "123");

        Map m1 = new HashMap();
        m1.put("name", "小小");
        m1.put("age", 21);
        m1.put("phone", "12");

        List l = new ArrayList();
        l.add(m);
        l.add(m1);

        for (Object e : l) {
    
            System.out.println(e);
        }
    }
}

3.用TreeSet比较学生的年龄大小。

package Java0910;

import java.util.Objects;

public class Student implements Comparable<Student> {
    {
    
    String name;
    int age;
    String phone;

    public Student(String name, int age, String phone) {
    
        this.name = name;
        this.age = age;
        this.phone = phone;
    }

    @Override
    public String toString() {
    
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", phone='" + phone + '\'' +
                '}';
    }

    @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 && Objects.equals(name, student.name) && Objects.equals(phone, student.phone);
    }

    @Override
    public int hashCode() {
    
        return Objects.hash(name, age, phone);
    }

    public int compareTo(Student o) {
    
        // return this.age-o.age; //从小到大
        return o.age - this.age;  //从大到小
    }
}

package Java0910;

import java.util.*;

public class List02 {
    
    public static void main(String[] args) {
    

        Student s = new Student("晓晓", 20, "15373412345");
        Student s1 = new Student("小小", 21, "132479069");

        Set l = new TreeSet();
        l.add(s);
        l.add(s1);

        for (Object e : l) {
    
            System.out.println(e);
        }
    }
}

4.创建一个比较器，实现Comparator接口

package Java0910;

import java.util.Comparator;

public class MyComparator implements Comparator<Student01> {
    
    @Override
    public int compare(Student01 o1, Student01 o2) {
    
        return o1.age - o2.age;
    }
}

package Java0910;

import java.util.Objects;

public class Student01 {
    
    String name;
    int age;
    String phone;

    public Student01(String name, int age, String phone) {
    
        this.name = name;
        this.age = age;
        this.phone = phone;
    }

    @Override
    public String toString() {
    
        return "Student01{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", phone='" + phone + '\'' +
                '}';
    }

    @Override
    public boolean equals(Object o) {
    
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Student01 student01 = (Student01) o;
        return age == student01.age && Objects.equals(name, student01.name) && Objects.equals(phone, student01.phone);
    }

    @Override
    public int hashCode() {
    
        return Objects.hash(name, age, phone);
    }
}

package Java0910;


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

public class TreeSet01 {
    
    public static void main(String[] args) {
    
        Comparator c = new MyComparator();

        TreeSet t = new TreeSet(c);

        Student01 s = new Student01("晓晓", 20, "15373412345");
        Student01 s1 = new Student01("小小", 21, "132479069");

        t.add(s);
        t.add(s1);
        for (Object e : t) {
    
            System.out.println(e);
        }
    }
}

5.匿名实现类

package Java0910;


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

public class TreeSet01 {
    
    public static void main(String[] args) {
    

        //匿名内部类(接口的实现类)
        TreeSet t = new TreeSet(new Comparator<Student01>() {
    
            @Override
            public int compare(Student01 o1, Student01 o2) {
    
                return o1.age - o2.age;
            }
        });

        Student01 s = new Student01("晓晓", 20, "15373412345");
        Student01 s1 = new Student01("小小", 21, "132479069");

        t.add(s);
        t.add(s1);
        for (Object e : t) {
    
            System.out.println(e);
        }
    }
}

6.lambad表达式

package Java0910;


import java.util.TreeSet;

public class TreeSet01 {
    
    public static void main(String[] args) {
    

        //lambad表达式
        TreeSet<Student01> t = new TreeSet<>((o1,o2) -> o1.age - o2.age);

        Student01 s = new Student01("晓晓", 20, "15373412345");
        Student01 s1 = new Student01("小小", 21, "132479069");

        t.add(s);
        t.add(s1);
        for (Object e : t) {
    
            System.out.println(e);
        }
    }
}