In which language are the Java compiler and JVM written?

Question

In which languages are the Java compiler (javac), the virtual machine (JVM) and the java starter written?

Answer 1

The precise phrasing of the question is slightly misleading: it is not "the JVM" or "the compiler" as there are multiple JVM vendors (jrockit is one, IBM another) and multiple compilers out there.

• The Sun JVM is written in C, although this need not be the case - the JVM as it runs on your machine is a platform-dependent executable and hence could have been originally written in any language. For example, the original IBM JVM was written in Smalltalk

• The Java libraries (java.lang, java.util etc, often referred to as the Java API) are themselves written in Java, although methods marked as native will have been written in C or C++.

• I believe that the Java compiler provided by Sun is also written in Java. (Although again, there are multiple compilers out there)

Answer 2

The very first Java compiler was developed by Sun Microsystems and was written in C using some libraries from C++. Today, the Java compiler is written in Java, while the JRE is written in C.

We can imagine how the Java compiler was written in Java like this:

The Java compiler is written as a Java program and then compiled with the Java compiler written in C(the first Java compiler). Thus we can use the newly compiled Java compiler(written in Java) to compile Java programs.

Answer 3

From Java Docs

The compiler is written in Java and the runtime is written in ANSI C

Answer 4

Actually the Oracle JVM is written in C++, not C.

Take a look at the HotSpot JVM code here: http://openjdk.java.net/groups/hotspot/

Answer 5

This link should answer your question

It seems the compiler is now written in Java, but the runtime is written in ANSI C

Answer 6

In principle almost anything, usually C

Answer 7

Jikes RVM, a self-hosting JVM used extensively for research purposes is written in Java. It's not the one people run on their desktops, but it's way up there on my list of "now let's show off the general power of the language."

Answer 8

Supposing you're talking about the Hotspot JVM, which is iirc provided by Sun, it is written in C++. For more info on the various virtual machines for Java, you can check this link. javac, like most Java compilers, is written in Java.

Answer 9

On most operating systems, JVMs are written in ISO C++. I doubt ANSI C is used, as it's an entirely different language that is quite antiquated nowadays.