How do I code using Java?

The compiler compiles the Java source code to a Java class file that contains the generated Java bytecode. The Java Virtual Machine (JVM) loads the class file and either interprets the bytecode or just-in-time compiles it to machine code and then possibly optimizes it using dynamic compilation. Most Java compilers, Jikes being the only exception, do virtually no optimization, leaving this until runtime to be done by the JRE. Even though each compiler uses a different technique, they all generate the same class file format.