Nowadays, Java has become the most popular and portable language for its "write once, run anywhere" promise, which makes it ideal for developing applications for ubiquitous devices. While the Java technology comes with compromises as well: the platform-independence is achieved via various JVMs, which are platform-specific; the execution speed of Java bytecode in JVMs is not as fast as native code written in C/C++. In this paper, we present a portable JVM and an asynchronous Java accelerator for ubiquitous devices. The JVM strives to be as cross-platform as possible by defining clear application programming interfaces between different modules and the Java accelerator was specially designed for accelerating execution of Java bytecode with low power consumption, which is critical to ubiquitous devices.