Access objects variable & method by name

Question

Example class:

class Test {
  public int marks;
  public String location;

  public String show(){
      return "Good morning!";
  }
}

Is there a way I can access marks and locations by a getter? Maybe like so:

Test t = new Test();
System.out.println(t.get("marks"));

and maybe

System.out.println(t.call("show"));

The exact use case I have is to be able to access R.id.[fieldname] for accessing Android Resource ID

Can this work ?

R.id.getClass().getField("date").get(R.id) ?

How could I do this ?

Reflection. I don't know off the top of my head, but a 5-minute googling will give you many useful answers. — gd1, Jun 05 '15 at 11:40
That is just perverse. Anyway, take a look at the Reflection APIs. — TEK, Jun 05 '15 at 11:41
What are you trying to achieve, at a much higher level? Because the answer is probably to do something other than what you're trying to do. public fields are a huge design smell. — JB Nizet, Jun 05 '15 at 11:41
You say "access by a getter'. In java that means to call a getter method, such as Rene M. suggested you. What you wrote in your example code is to call by a method name / access by variable name. You should not do it, unless you are sure that you need it. — AdamSkywalker, Jun 05 '15 at 11:52
If its going about R class in android. Better look here: http://stackoverflow.com/questions/3476430/how-to-get-a-resource-id-with-a-known-resource-name Specialy this part: "public int getIdentifier (String name, String defType, String defPackage) " — Rene M., Jun 05 '15 at 13:13

score 3 · Accepted Answer · answered Jun 05 '15 at 11:41

3

Test t = new Test();
System.out.println(t.getClass().getField("marks").get(t));

answered Jun 05 '15 at 11:41

Oh, very nice ! Is there a way to call a method as well ? Maybe getMethod ? – Prakash Raman Jun 05 '15 at 11:42
@PrakashRaman sure. Here's the API about reflection: http://docs.oracle.com/javase/tutorial/reflect/index.html . – Jun 05 '15 at 11:46
http://stackoverflow.com/questions/20738583/how-to-call-a-function-of-class-from-a-different-class-using-reflection-in-java/20738825#20738825 – Karthigeyan Vellasamy Jun 05 '15 at 11:52
Thanks, although it does not seem to work on the Android "R.id" could you see the edited question. – Prakash Raman Jun 05 '15 at 12:03

score 2 · Answer 2 · answered Jun 05 '15 at 11:54

2

To invoke a method and get its value from some other class use this

Method method = obj.getClass().getMethod("Methodname", new Class[] {});
String output = (String) method.invoke(obj, new Object[] {});

answered Jun 05 '15 at 11:54

2 Answers2