JavaScript is an object-oriented scripting language that allows you to create dynamic HTML pages, allowing you to process input data and maintain data, usually within the browser.
Java is a programming language, core set of libraries, and virtual machine platform that allows you to create compiled programs that run on nearly every platform, without distribution of source code in its raw form or recompilation.
While the two have similar names, they are really two completely different programming languages/models/platforms, and are used to solve completely different sets of problems.
Also, this is directly from the Wikipedia Javascript article:
A common misconception is that JavaScript is similar or closely related to Java; this is not so. Both have a C-like syntax, are object-oriented, are typically sandboxed and are widely used in client-side Web applications, but the similarities end there. Java has static typing; JavaScript's typing is dynamic (meaning a variable can hold an object of any type and cannot be restricted). Java is loaded from compiled bytecode; JavaScript is loaded as human-readable code. C is their last common ancestor language.
