C compiler

Hello,
whats up guys... i have just started using Ubuntu... what Good compiler for C,C++,C# and Java can i Use

gcc for the first three (should be part of the default setup, if not install from the package manager), Oracle JDK for Java. A good IDE is Eclipse, which will handle all of those.

Edit: Oops, not gcc for C#. You'll need mono for that. C# is not really a good language for Linux development (IMO), though it's one of the best Windows languages.

C/C++ can be handled by GCC, which is installed by default.
C# is covered by the Mono project, but you should leave that in Windows.
Java, you can download the Oracle JDK.

You can use Gedit/Nano/ViM, which are installed by default, or install an IDE such as Eclipse or Netbeans. Entirely up to you.

Since the only disagreement seems to be the IDE, let me throw in Anjuta as another one to consider. Fairly lightweight but quite powerful.

LLVM in technically the bottom-end of a compiler framework, and as such there's a llvmgcc project that has some fairly-impressive compiletime speedups (and even results in faster code at times due to a wider frame in which to optimize).

LLVM works on a model that describes your program, so in theory it can be used to compile from any language with an appropriate language-to-model adapter layer, for example the company that I work for uses LLVM under the hood to convert graphical "programs" to the graph representation on which LLVM operates (and therefore makes it easier to target various different architectures)