A distributed Java virtual machine called SingleJava based on thread migration is proposed in this paper. SingleJava can be used to build a distributed computing framework while keeping itself completely transparent to Java programmers. The main idea underlying is to improve the inevitable Java virtual machine in a Java based software system, i.e., adding a build-in distributed infrastructure to the virtual machine and integrating it into a distributed computing framework. Meanwhile, traditional distributed program are usually difficult to test or debug. SingleJava supports testing and debugging applications on a single node Java virtual machine, such as Oracle Hopspot or IBM J9, and the applications or compiled classes can be deployed directly to the distributed SingleJava infrastructures.