Hashmap使用2

Hashmap使用2

package com.tiedandan.集合.Map集合.HashMap使用2;

import com.tiedandan.集合.Map集合.HashMap使用.Student;

import java.util.HashMap;
import java.util.Map;

/**
 * 去除添加
 *
 */
public class HashMapUse {
    public static void main(String[] args) {
        HashMap<Student, String> students = new HashMap<>();//键类型是student，值类型是String类型
        Student stu1 = new Student("唐僧",1);
        Student stu2 = new Student("孙悟空",2);
        Student stu3 = new Student("猪八戒",3);
        Student stu4 = new Student("沙和尚",4);
        students.put(stu1,"天宫");
        students.put(stu2,"花果山");
        students.put(stu3,"高老庄");
        students.put(stu4,"流沙河");
        students.put(new Student("沙和尚",4),"流沙河");//要想使重复的·对象不会加入到集合当中，需要重写HashCode和equals方法

        System.out.println("键值对个数："+students.size());
        System.out.println("========输出键值对的值==========");
        System.out.println(students.toString());
        //删除
//        students.remove(stu4);
        //遍历
        //使用KeySet();
        System.out.println("----------使用KeySet();----------");
        for (Student student : students.keySet()) {
            System.out.println(student.toString()+"--------"+students.get(student));
        }

        //使用entryset();
        System.out.println("--------------使用entryset();-----------");
        for (Map.Entry<Student, String> entry : students.entrySet()) {
            System.out.println(entry.getKey()+"----"+entry.getValue());

        }
        //判断
        System.out.println("-------判断--------");
        System.out.println( students.containsKey("沙和尚"));
        System.out.println( students.isEmpty());

    }
}

Student类：

package com.tiedandan.集合.Map集合.HashMap使用2;

import java.util.Objects;

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

    public Student() {
    }

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

    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;
    }

    @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);
    }

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

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

　　运行结果：

键值对个数：5
========输出键值对的值==========
{Student{name='猪八戒', age=3}=高老庄, Student{name='沙和尚', age=4}=流沙河, Student{name='孙悟空', age=2}=花果山, Student{name='唐僧', age=1}=天宫, Student{name='沙和尚', age=4}=流沙河}
----------使用KeySet();----------
Student{name='猪八戒', age=3}--------高老庄
Student{name='沙和尚', age=4}--------流沙河
Student{name='孙悟空', age=2}--------花果山
Student{name='唐僧', age=1}--------天宫
Student{name='沙和尚', age=4}--------流沙河
--------------使用entryset();-----------
Student{name='猪八戒', age=3}----高老庄
Student{name='沙和尚', age=4}----流沙河
Student{name='孙悟空', age=2}----花果山
Student{name='唐僧', age=1}----天宫
Student{name='沙和尚', age=4}----流沙河
-------判断--------
false
false