Java中Map集合遍历的两种方式比较及其图解

1. Map集合变量之键找值

		HashMap<String,String> hm = new HashMap<>();
        String s1 = hm.put("张三","北京");
        String s2 = hm.put("李四","上海");
        String s3 = hm.put("王五","深圳");
        String s4 = hm.put("赵六","上海");
        Set<String> set = hm.keySet();
        Iterator<String> iterator = set.iterator();
        while (iterator.hasNext()) {
    
    
            String key = iterator.next();
            String value = hm.get(key);
            System.out.println(key + "   " + value);
        }

简化

        for (String s:
             hm.keySet()) {
    
    
            System.out.println(s + "   " + hm.get(s));
        }

2. Map集合遍历之键值对对象找键和值

        HashMap<String,String> hm = new HashMap<>();
        String s1 = hm.put("张三","北京");
        String s2 = hm.put("李四","上海");
        String s3 = hm.put("王五","深圳");
        String s4 = hm.put("赵六","上海");
        Set<Map.Entry<String,String>> entrySet = hm.entrySet();
        Iterator<Map.Entry<String,String>> iterator = entrySet.iterator();
        while(iterator.hasNext()) {
    
    
            Map.Entry<String,String> entry = iterator.next();
            String s = entry.getKey() + "   " + entry.getValue();
            System.out.println(s);
        }

简化

        for(Map.Entry<String,String> entry: hm.entrySet()) {
    
    
            System.out.println(entry.getKey() + "   " + entry.getValue());
        }