Your browser should have the option to disable Java plugin.
Under the Plug-ins section of the settings url: chrome://settings/content select "Block All".
With this option enabled, when you want to run plugins on a page you have 3 options:
1.Right click on the plugin and choose "Run this plug-in" from the context menu
2.Click the plugin icon in the URL bar and choose "Run all plug-ins this time
3.Add an exception for sites you trust so that they can run plugins without your explicit permission each time
Source - Dan Herbert
By default, Firefox allows Java applets to launch automatically. However, you may decide that you do not want Java applets to run. To disable Java applets in Firefox:
1.At the top of the Firefox window, click on the Firefox button (Tools menu in Windows XP), and then click Add-ons. The Add-ons Manager tab will open.
2.In the Add-ons Manager tab, select the Plugins panel.
3.Click on the Java (TM) Platform plugin to select it.
4.Click on the Disable button (if the button says Enable, Java is already disabled).
Java applets will no longer be permitted to launch in Firefox.
If you want to remove Java from your system, simply remove the packages you have installed.
To search Java packages, in a console type
dpkg -l java