Map简单应用

Map是以键值对的形式来存储数据的Map

public class Demo02 {    public static void main(String[] args) {        Map<String, Double> m = new HashMap<>();        m.put("张三", 59.0);        m.put("张三1", 59.0);        m.put("张三3", 59.0);        m.put("张三2", 85.0);        System.out.println(m);        /*         * 通过key组成的Set集合遍历map         */        //1、获取mao中所有key组成的Set        Set<String> s = m.keySet();        //2、对这个keySet进行遍历        Iterator<String> it = s.iterator();        while (it.hasNext()) {            String str =  it.next();            System.out.println(m.get(str));         }    }}

如果存放的是对象：
Student.java

public class Student {    private String name;    private int age;    private String sex;    private double score;    public Student(String name, int age, String sex, double score) {        super();        this.name = name;        this.age = age;        this.sex = sex;        this.score = score;    }    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 String getSex() {        return sex;    }    public void setSex(String sex) {        this.sex = sex;    }    @Override    public String toString() {        return "Student [name=" + name + ", age=" + age + ", sex=" + sex                + ", score=" + score + "]";    }    public double getScore() {        return score;    }    public void setScore(double score) {        this.score = score;    }}

Teacher.java:

public class Teacher {    private String name;    public Teacher(String name) {        super();        this.name = name;    }    public Teacher() {        super();    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    @Override    public String toString() {        return "Teacher [name=" + name + "]";    }}

Main.java

package com.zhongbei.www.map02;import java.util.HashMap;import java.util.Map;import java.util.Map.Entry;import java.util.Set;public class TheMainClass {    public static void main(String[] args) {        Map<Student, Teacher> map = new HashMap<Student, Teacher>();        map.put(new Student("小狄", 15, "女",3), new Teacher("Great Song"));        map.put(new Student("王鹏", 5, "女",15), new Teacher("Bo Li"));        map.put(new Student("小人", 15, "不详", 65), new Teacher("老王"));        map.put(new Student("小杰", 16, "男", 95), new Teacher("sam"));        Set<Entry<Student, Teacher>> entrySet = map.entrySet() ;        for (Entry<Student, Teacher> e : entrySet) {            //e就是键值对组成的对象。            //可以通过e取出键值对的键和值            Student s = e.getKey();            Teacher t = e.getValue();            System.out.println(s);            System.out.println(t);        }    }}