Rahul Garg Rahul Garg - 7 months ago 17
Java Question

In which language are the Java compiler and JVM written?

In which languages are the Java compiler (

javac
), the virtual machine (JVM) and the
java
starter written?

Answer

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)

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