How can I step into a core java class method in Eclipse?

Question

Hi I am going to dig a little more in Java so I would like to see how the program executed in the core class. For example, I would like to know how String.chatAt()

Answer 1

Most likely, you have the "Step filtering" functionality activated.

When debugging, it can sometimes be a bit annoying when the debugger steps into trivial classes whose internals you were not really interested in. Because of this, you can configure "Step filters". Classes or packages that are added as step filters will be ignored by the "Step into" operation.

If you want to configure which classes/packages should be included in the step filter, you can go to:
Window --> Preferences --> Java --> Debug --> Step Filtering
My guess is that you have a java.* package filter defined there, meaning that the debugger will never step into any class within a package which starts with "java". Uncheck this package filter if you want to be able to step into java.lang.String

Alternatively, if you want to activate/deactivate step filtering completely, you can do this by clicking the Use step filtering button in the debug view, as shown below: