遍历Map的三种方式

遍历Map的三种方式

public static void main(String[] args) {
        
        Map<String,String> map = new HashMap<>();
        map.put("1","第一个参数");
        map.put("2","第二个参数");
        map.put("3","第三个参数");
        map.put("4","第四个参数");

        //迭代器遍历
        Iterator<Map.Entry<String,String>> it = map.entrySet().iterator();

        while (it.hasNext()) {
            Map.Entry<String, String> entry = it.next();
            System.out.println("key="+entry.getKey()+",value="+entry.getValue());
        }

        //keySet遍历
        for (String key:map.keySet()){
            System.out.println("key="+key+",value="+map.get(key));
        }

        //entrySet遍历
        for (Map.Entry<String,String> entry:map.entrySet()){
            System.out.println("key="+entry.getKey()+",value="+entry.getValue());
        }
    }

推荐使用entrySet遍历，因为keySet遍历的时候需要通过key取出值效率有所下降