In C# .net there is a provision to have two different class files and make them a single class using the keyword partial keyword.this helps it to keep [for ex]UI and logic seperate. of course we can have two classes to achieve this one for UI and other for logic. Can this be achieved in java some how?
No. Java source codes can not be split across multiple files.
From the Wikipedia article Comparison of Java and C Sharp
The Sun Microsystems Java compiler requires that a source file name must match the only public class inside it, while C# allows multiple public classes in the same file, and puts no restrictions on the file name. C# 2.0 and later allows a class definition to be split into several files, by using the partial keyword in the source code. In Java, a public class will always be in its own source file. In C#, source code files and logical units separation are not tightly related.
The two classes approach is a much better solution than the one-class-two-source approach in this case, because the separation is enforced in the design, not just physical separation in the source codes.