Why is javac source code is written in java? [closed]

Question

I have downloaded the javac source code from here and I found that the it itself is written in java language. However, I was expecting that it was written in c/c++.

Anyway, how does this java compiler source code written in java compiled when there was no java compiler?

Answer 1

From here :

The very first Java compiler developed by Sun Microsystems was written in C using some libraries from C++

Besides the compiled bytecode is interpreted by JVM which is written in c++. From here:

The Oracle JVM, named HotSpot, is written in the C++ language

Answer 2

A compiler that is written in the language it compiles is called a bootstrapping compiler.

The way they are made is kind of a head trip, but just think: when the original language was written, there was no java, and so they had to create the compiler in another language, which, actually, was written in C/C++. Check it out, here: In which language are the Java compiler and JVM written?

Also, the way that Java works, I don't know if you know, is that the compiler (javac) actually doesn't generate machine code files, it creates bytecode files that are then interpreted by the JVM.

Answer 3

You usually need an existing Java compiler (and runtime) to bootstrap. However, there are other Java compilers available, like Jikes, that are written in C++. Whether you can use Jikes to bootstrap OpenJDK is a different story, but in theory, it should be possible.