first compile your code by 
javac "File name"
then run the byte code by 
java Main

Types in java 
    - Primitive Types: "for simple simple value",
                        type Byte Range
                        byte 1 - 128
                        short 2  - 32k
                        int 4 - 2B
                        long 8 
                        float 4
                        double 8
                        char 2  A, B, C, ...
                        Boolean 1 true/false
    - Reference Types: "for storimg complex objects"