If you have a Java variable named xyz. Then later on I define a string which has the value of the named variable I want to play with.
String x="xyz";
How do I get Java to recognise that String x as a pointer to variable xyz?
An arbitrary example:
JButton a= new JButton();
Later on ...
String x="a";
I want to now say something like
JButton called string x.setPreferredSize(new Dimension(40,30));
In general, if you want to access a variable in this way, you have to use Reflection, which is slower and potentially dangerous.
However, since you have a very specific scenario in mind, I'd take a different approach. Why not put your buttons or other elements into a map, with keys that are strings:
Map<String, JComponent> currentComponents = new HashMap<String, JComponent>();
currentComponents.put("a", new JButton());
String x = "a";
currentComponents.get(x).setPreferredSize(new Dimension(40,30));
The short answer is that you can't do something like this. That just isn't the way the Java language works. The long answer is that you might be able to simulate something using the Reflection API.
