java Map删除值为null的元素

Map<String, String> params=new HashMap<>();
params.put("ccc","null");
params.put("bbb","");
params.put("aaa",null);
params.put("ggg",null);
Iterator<Map.Entry<String, String>> it = params.entrySet().iterator();
while(it.hasNext()){
    Map.Entry<String, String> entry = it.next();
    if(entry.getValue() == null)
        it.remove();//使用迭代器的remove()方法删除元素  
}

Map<String, String> params=new HashMap<>();
params.put("ccc","null");
params.put("bbb","");
params.put("aaa",null);
params.put("ggg",null);
// 一行lamada表达式   
params.entrySet().removeIf(entry -> entry.getValue() == null);