How to open the saved. Java file in command prompt?

Answer 1

you compile it first with:
javac FileName.java
run with:
java FileName

Each time you make a change to the file, you'll need to recompile

Answer 2

type .java in command prompt

Answer 3

you just need to write file name in the command prompt with extension .java. file will be open.
and for compilation and execution of that file you have to use these commands
compile: javac filename.java
run : java filename