package com.oracle.containers.map;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
/**
 * @author zhouyanxiang
 * @create 2020-08-2020/8/17-10:13
 */
public class HashMapReview {
    public static void main(String[] args) {
        HashMap <String,String> map = new HashMap<>();
        map.put("Tom","23");
        map.put("Jerry","24");
        map.put("Mike","29");
        map.put("Mary","22");
        map.put("Bruce","20");
        map.put("Jerry","24");
        // 如果有相同的并不会算进map.size里面去
        System.out.println(map.size());
        // 遍历HashMap的四种方式
        System.out.println("====== No1 ======");
        // 第一种 通过Map.keySet遍历key和value
        System.out.println("通过Map.keySet遍历key和value");
        for (Object key:map.keySet()){
            System.out.println("key : " + key + " value: " + map.get(key));
        }
        System.out.println("====== No2 ======");
        // 第二种
        System.out.println("通过Map.entrySet使用iterator遍历key和value");
        Iterator it = map.entrySet().iterator();
        while (it.hasNext()){
            Map.Entry<String, String> entry = (Map.Entry<String, String>) it.next();
            System.out.println("key : " + entry.getKey() + " value: " + entry.getValue());
        }
        System.out.println("====== No3 ======");
        // 第三种 推荐，尤其是容量大时  通过Map.entrySet遍历key和value
        System.out.println("通过Map.entrySet遍历key和value");
        for (Map.Entry<String, String> entry : map.entrySet()){
            System.out.println("key : " + entry.getKey() + " value: " + entry.getValue());
        }
        System.out.println("====== No4 ======");
        System.out.println("通过Map.values()遍历所有的value，但不能遍历key");
        for(String v:map.values()) {
            System.out.println("value: " + v);
        }
    }
}