Esmertec's Jbed Java, Aicas Jamaica, Java 2 Mobile Edition (J2ME), and JSR-01 are highlighted in a discussion of Sun Microsystems Java language's advancement from a language to a an object-oriented environment that provides cautious memory management, stringent type checking, and security abilities that are not provided in such languages as C and C++. An expert says Java programmers can have about twice the productivity of C++ developers, and that Java does automatic garbage collection and encapsulation so that implementation details can be hidden easily. Segmentation faults and stack overflow bugs are eliminated. Later versions of Java include J2EE and J2ME, and J2ME is available in connected Device Configure (CDC) and Connected Limited Device Configure (CLDC) versions. The CDC version is in embedded devices such as printers, and the CLDC version is in smaller devices, including cellphones. Each platform has a VM that interprets and runs the Java byte code. Sun usually sells J2ME source-code products to vendors who customize a VM for their processes or boards. When embedded developers need real-time performance, they can use JSR-01 (Real-Time Specification for Java/(RTSJ). For instance, the Jamaica VM Java virtual machine from Aicas combines with the RTSJ specification and allows developers to compile Java programs into machine code for high-speed execution. Esmertec's Jbed Java can also be used by Developers who plan to embed a Java runtime engine and its extensions in handsets, set-top boxes, or machine-to-machine devices.