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Map接口实现类:TreeMap

时间:2020-07-08 17:38:15      阅读:53      评论:0      收藏:0      [点我收藏+]

TreeMap

示例代码:

public class Student implements Comparable<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 String toString() {
        return "Student{" +
                "name=‘" + name + ‘\‘‘ +
                ", 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 int compareTo(Student o) {
        int n2 = this.age - o.age;
        int n1 = this.name.compareTo(o.getName());

        return n1==0?n2:n1;
    }
}

/**
 * HashMap集合的使用
 * 存储结构:哈希表(数组+链表+红黑树)
 * 使用Key的hashcode和equals作为重复依据
 */
public class Demo {
    public static void main(String[] args) {

        //创建集合
        TreeMap<Student,String> student = new TreeMap<>();
        //1.添加
        Student s1 = new Student("a",1);
        Student s2 = new Student("b",2);
        Student s3 = new Student("c",3);
        student.put(s1,"beijing");
        student.put(s2,"shanghai");
        student.put(s3,"shenzhen");
        student.put(new Student("c",3),"nanjing");
        System.out.println(student.size());
        System.out.println(student.toString());

        //2.删除
        //student.remove(s1);
//        student.remove(new Student("b",2));
//        System.out.println(student.size());
//        System.out.println(student.toString());;

        //3.遍历
        //3.1使用keySet
        for (Student s:student.keySet()){
            System.out.println(s+":"+student.get(s));
        }
        System.out.println("---------------------------");
        //3.2使用entrySet
        for (Map.Entry<Student,String> s:student.entrySet()){
            System.out.println(s.getKey()+":"+s.getValue());
        }

        //4.判断
        System.out.println(student.containsKey(s1));
        System.out.println(student.containsKey(new Student("b",2)));
    }
}

Map接口实现类:TreeMap

原文:https://www.cnblogs.com/qiudajiang/p/13267942.html

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