Java is a program that may be useful for some web site (online games). Java applets allow code execution on your PC and access to your system. Running a malicious applet thus represents a security risk. Java is also installed in your web browser and if the version is not updated, it allows the infection (automatically) of your computer via exploits on malicious web site.
To disable Java from your Web browsers: Method 1: Via the Control Panel (Java Console)
Method 1: Disable the Java plug-in of Internet Explorer.