How to test whether the value of a Java field gotten by reflection is null?

问题

I have

Field f = this.getClass().getFields()[0];

I need to know if f's value in this is null or not. There are many methods like getInt() and getDouble(), but I have not found a method like Object getData() or isNull(). Is there such a method?

回答1:

field.get(target) returns Object. So you can checkif (field.get(this) == null) {..}

If the field is primitive, it will get wrapped. int -> Integer, char -> Character, etc.

回答2:

You need to get the field from the object then check if it is null

Field f = this.getClass().getFields()[0];
if (f.get(this) == null)
  ...

回答3:

You didn't search well enough: http://download.oracle.com/javase/6/docs/api/java/lang/reflect/Field.html#get%28java.lang.Object%29

Call this method, and check if the returned object is null.

回答4:

use Object obj=f.get(this) and check whether the returned object(in this case obj) is null or not

来源：https://stackoverflow.com/questions/8228207/how-to-test-whether-the-value-of-a-java-field-gotten-by-reflection-is-null