what topic or api in java,do i need to be good at to arrive in java programming?

You have to cover the basics.Below is the link to the official java tutorial from sun's website http://download.oracle.com/javase/tutorial/ ].Look through the page and you will see the Trails Covering the Basics & Creating Graphical User Interfaces section.those are enough to get you started.however it is good to combine these with java books written by professionals such as thinking in java and deitel & deitel's java:how to program.Now,if you are good in any other programming language,all you need is to port your knowledge of that language to java and find out how the whole oop concept is implemented in java if the language you know is oop,if not,you will still see basic programming concepts you know except that this time around you will be dealing with objects and classes and oop concepts like inheritance,abstraction,polymorphism and encapsulation.if you are new to programming,you will have to take the initial step i outlined.

Good luck!

Charles Leiserson said in one of his lectures few years ago at MIT and i quote:

To be a world class programmer, program everyday for 10yrs , [few seconds of silence], or program everyday for 2years and take an algorithms and data structures class

But note as naija_swag said, you have to start from the basics.

Pls what type of app can you create with java.

The kind that can support a java device

a) Discrete Mathematics(To get you started)

b) Combinatorics

c) Set Theory

d) Mathematical Logic

e) Data Structures

f) Algorithms

g) Number theory(if you plan to explore cryptography)

Not necessarily in the order listed but certainly, if you want to be an expert in Java or any other programming Language, then you should get to working on the list above

Wexelion:

Pls what type of app can you create with java.

Think this way instead. If you have the knowledge necessary, you can create anything with Java.

Kobojunkie:

a) Discrete Mathematics(To get you started)

b) Combinatorics

c) Set Theory

d) Mathematical Logic

e) Data Structures

f) Algorithms

g) Number theory(if you plan to explore cryptography)

Not necessarily in the order listed but certainly, if you want to be an expert in Java or any other programming Language, then you should get to working on the list above

not only those stuffs, you got to be a prof in math b/4 you start java lang.

^^^^ Contrary to what you  think there, the average computer scientists ought to at least have base knowledge in most all those areas listed. Unless you intend to be a code-churner which majority really are --- good at reproducing the same codes/logic, year after year, mostly driven by money and not much else.

NB: That list says nothing specific about the language, or any other language for that matter. That is really how to become a guru -- not to focus on the language but computer science itself.

I agree. If you get a good grasp of the core concepts, then it will make developing solutions to problems easy. Regardless of programming language. The programming language you use is just one of the several tools out there that can be used to implement the solution. What matters is coming up with a solid solution.

nakedall:

not only those stuffs, you got to be a prof in math b/4 you start java lang.