Map打印

1.使用entries来遍历,如果遍历的map是一个空值，循环会抛出NUllPointerException

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

2.使用keySet

for(String key : map.keySet()){
	System.out.print("Key = "+key+"value = "+map.get(key));
 }