Compiled versus Interpreted

• Interpretors run source program, "interpreting" the source code on the fly.
• Compilers translate the source program to machine language.
  • Well, actually, they usually translate it to object code.
  • The object code is "linked" with other code by a linker.
• Speed
  • Compilers win
  • Optimizing compilers really win
  • (In Java automatic garbage collector runs as a low-priority background thread e.g. improves response.)
• Security, viruses etc.
  • Fully interpreted languages win
• Java is interpreted.
  • Well, actually, it's compiled to "bytecodes".
  • Bytecodes are interpreted by a virtual machine.
  • The virtual machine is emulated by the Web browser.
• Java is a trade off between speed and security.

Bytecode generation and interpretation. Lifted from The Java(tm) White Paper (Sun Microsystems).