A Java compiler is a compiler for the Java programming language.
Some Java compilers output optimized machine code for a particular hardware/operating system combination, called a domain specific computer system. An example would be the now discontinued GNU Compiler for Java.
The most common form of output from a Java compiler is Java class files containing cross-platform intermediate representation (IR), called Java bytecode.
The Java virtual machine (JVM) loads the class files and either interprets the bytecode or just-in-time compiles it to machine code and then possibly optimizes it using dynamic compilation.
A standard on how to interact with Java compilers was specified in JSR 199.
It is provided by module <code>jdk.compiler</code>, and requires the full Java Development Kit (as opposed to just the Java Runtime Environment), and reside in the <code>javax.tools.*</code> namespace.