With JIT the java command takes the bytecode and compiles it again to the native instructions for the CPU it is running on. To improve this Just in Time (JIT) compilation was added to the Java Runtime. This worked but wasn't particularly fast. class file and interpret the bytecode instructions one at a time and then map them to the equivalent native instruction for what ever CPU it was actually running on. When Java was first launched the java command would read the. Because of this it is close to lots of different types of CPU making it easier to run the same Java. This virtual CPU specification is sort of an average of types of CPUs that were common at the time the specification was written. Bytecode is a the machine code (native instructions) for a theoretical CPU based on the Java Virtual Machine specification.

class file the output is something called bytecode. When you use the javac command to compile a. Yes, but not in the way you probably mean.

The motivation for JEP 330 was to make it easier for 'early stages of learning Java, and when writing small utility programs' without changing any other existing uses.

class files so that code can be created, tested, distributed, run, shared, etc. (to execute a single source-file program) The last one is what you ran into: java which will 'execute a single source-file program'. If you run java -help, you'll see the various allowed usages. Since Java 11, you can still do javac + java, or you can run java by itself to compile and auto-run your code. Prior to Java 11, to run your code you have to first compile it, then you can run it.

Compiling java file