How to access a class variable by passing value to object from another variable?

Question

I was wondering, if it's possible to call a variable of other class by passing value to object from another variable.

Something like this:

class Foo {
   public String classVar = "hello";
} 

then we make a object of the class :

Foo bin = new Foo();

Now, I know we can use var by :

bin.classVar;

But, suppose value classVar is in another string variable :

Foo bin = new Foo();    
String var2 = "classVar";
bin.var2 ??????????

How to achieve this?

Answer 1

Variable names are statically typed in Java. You cannot made them dynamically like this. You can use reflection, if you really need it.

Answer 2

You can use Reflections to get it.

Foo bin = new Foo();    

Now, Foo has a variable "classVar".

So, you do:

Field f1[] = Foo.class.getDeclaredFields();
for(Field f:f1)
{
     if(f.getName().equals("classVar"))
         System.out.println(f.get(bin)); //Get the value
}

Answer 3

You can achieve that by using Reflection with just one line of code in a try-catch block, like below:

try {
        var2 = (String) bin.getClass().getField("classVar").get(bin);
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

PS Using reflection generally can be risky if not controlled well. But it will amazingly increase your coding flexibility, if it is handled carefully.