map集合修改其中元素

package com.swift.lianxi;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

/*1.请简述Map 的特点
2.请简述HashMap的特点
3.请简述LinkedHashMap的特点
4.使用代码依次完成：
    a).将如下键值对信息存入Map集合中:
        "黄晓明", "Baby"
        "邓超", "孙俪"
        "李晨", "范冰冰"
        "大黑牛", "范冰冰"
    b).将"李晨"对应的值替换成"白百合"
    c).获取"大黑牛"对应的值，如果是"范冰冰"就删除以"大黑牛"为键的元素

5.使用代码完成：往一个Map集合中添加若干元素.获取Map中的所有key, 并使用增强for和迭代器遍历输出每个key
6.使用代码完成：往一个Map集合中添加若干元素.获取Map集合中所有的键值对(Entry)对象, 并使用增强for和迭代器遍历输出每个key和value
7.使用代码完成：将学员的信息作为元素存入HashMap中，
    提示：1.每位学生（姓名，年龄）都有自己的家庭住址
        2.将学生对象和家庭住址存储到map集合中。学生作为键, 家庭住址作为值。
         3.学生姓名相同并且年龄相同视为同一名学生*/

public class Demo1 {

    public static void main(String[] args) {

        HashMap<String, String> map = new HashMap<String,String>();
        map.put("黄晓明", "Baby");
        map.put("邓超", "孙俪");
        String str1=map.put("李晨", "范冰冰");
        map.put("大黑牛", "范冰冰");
        System.out.println(map);
        //如果键值相同,直接put就是替换
        String str2=map.put("李晨", "白百合");
        System.out.println(map);
        System.out.println(str1+"..."+str2);
        String str3=map.get("大黑牛");
        if("范冰冰".equals(str3)) {
            map.remove("大黑牛");
        }
        System.out.println(map);

        System.out.println("===========================================");
        //keySet使用增强for遍历
        Set<String> keys = map.keySet();
        for(String key:keys) {
            System.out.println(key+"..."+map.get(key));
        }
        //keySet使用iterator遍历
        System.out.println("===========================================");
        Set<String> set =map.keySet();
        Iterator<String> it=set.iterator();
        while(it.hasNext()) {
            String name = it.next();
            System.out.println(name+"..."+map.get(name));
        }
        //entrySet使用增强for遍历
        System.out.println("===========================================");
        Set<Map.Entry<String,String>> entry = map.entrySet();
        for(Map.Entry<String, String> key:entry) {
            System.out.println(key.getKey()+"..."+key.getValue());
        }
        //entrySet使用iterator遍历
        System.out.println("===========================================");
        Set<Map.Entry<String,String>> set1 =map.entrySet();
        Iterator<Map.Entry<String,String>> it1=set1.iterator();
        while(it1.hasNext()) {
            Map.Entry<String,String> entry1= it1.next();
            System.out.println(entry1.getKey()+"..."+entry1.getValue());
        }

        HashMap<Student, String> students = new HashMap<Student,String>();
        students.put(new Student("zhangsan",20), "北京");
        students.put(new Student("lisi",21), "上海");
        students.put(new Student("wangwu",22), "广州");
        students.put(new Student("zhaoliu",23), "深圳");
        students.put(new Student("zhaoliu",23), "香港");
        for(Student stu:students.keySet()) {
            System.out.println(stu.toString()+"..."+students.get(stu));
        }
    }

}

class Student{

    private String name;
    private int age;
    private String address;
    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 getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    public Student(String name, int age, String address) {
        super();
        this.name = name;
        this.age = age;
        this.address = address;
    }
    public Student(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }
    public Student() {
        super();
        // TODO Auto-generated constructor stub
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((address == null) ? 0 : address.hashCode());
        result = prime * result + age;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Student other = (Student) obj;
        if (address == null) {
            if (other.address != null)
                return false;
        } else if (!address.equals(other.address))
            return false;
        if (age != other.age)
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }
    @Override
    public String toString() {
        return "Student [name=" + name + ", age=" + age + ", address=" + address + "]";
    }

}

原文地址：https://www.cnblogs.com/qingyundian/p/8495079.html