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)
Go to the Control Panel.
Double-click on Java.
On the Security tab, un-check: Enable Java content in the browser.
Method 1: Disable the Java plug-in of Internet Explorer.
Open Internet Explorer.
Tools / Manage Add-ons.
Go to Tools and extensions, select Java and then click Disable.
Just disable the Java plugin: Tools > Add-ons > Plugins tab.
Look for Java and click Disable.
Note that: Firefox can automatically disable plugins that may pose security problems (not updated).
Open Google Chrome and in the address bar type: about:plugins or chrome://plugins.
In the list, find Java and click Disable.
Note that: If your version of Java obsolete, Google Chrome will notify you with the message "Java Plug-in was blocked because it is obsolete" each time you open an applet.
Open your browser
Click on the Opera button at the top of your window
In the menu that appears, go to "More tools" and click "Enable developer tools".
Close and restart your browser
Click again on the Opera button > Developer tools > Plug-ins.