Why we only use blue j for java programms

Question

I only want to know about it as how previous
people do programma when blue j was not there

Answer 1

:O
You'll at least need the JDK (else nothing's gonna work). Here's a way to run a Java program from command prompt.
http://www.codejava.net/java-core/how-to-write-compile-and-run-a-hello-world-java-program-for-beginners

Answer 2

There are many alternatives available like Eclipse and IntelliJ IDEA. Look here for more:
https://blog.idrsolutions.com/2015/03/the-top-11-free-ide-for-java-coding-development-programming/

Answer 3

ok now I got that and thanks I will ask more and please clear my doubts then also

Answer 4

no no I want to know that with no software only with OS