0 What is Java Compiler?

The java compiler is the program which compiles a .java file into byte code (.class files).

       As you all know, the source code of Java will be stored in a text file with extension .java, the Java compiler compiles the .java file into byte code which will be in a file with extension .class

       Byte Code is NOT in the machine language format of the hardware platform on which the code is compiled, that means the hardware processor cannot understand the byte code (Languages like C compiles the program into the machine language format of the hardware platform on which it is running). Instead, the byte code is in the machine language format of a machine known as the Java Virtual Machine or the JVM. That means you always need a JVM to execute the byte code.

       JVM is not a real machine, it is just a virtual machine; implemented in software.