You might want to try installing version 1.7 (oracle's one, not openjdk), and making sure it is the active version using update-alternatives and java -version.
Do note, however, that java is NOT a fast technology. Your applications are compiled to intermediate bytecode which needs to be interpreted by a fairly heavy application called the JVM. Although I don't remember ever having experienced multiple seconds of interface lag, I do know the GUI's written in java tend to be slow.
I've never noticed any difference between windows 7 and ubuntu/opensuse though (each 64-bit), but that might be due to the version: I always get the latest official java sdk (that is, from Oracle).
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Although this might not be the answer you'd like to hear, if you don't explicitely need java (which you would if you were targetting mobile devices, I suppose) and/or if performance is important for your application, you might want to look for a native-compiled alternative. C++ with Qt would be an excellent alternative, if you're familiar with C++. It keeps your application cross-platform, without affecting the general performance.
Mono/C# comes with an option to precompile the bytecode, so you basicly have a native executable with the mono runtime included (heavy at startup, but faster than java at runtime).
