How To install java in Ubuntu

To install Propriety Java in Linux Box.so first Download Jdk from Oracle java site and Downlaod jdk-7.x.x.tar,gz file.
    and extract tar.gz file using tar command
        tar -xvzf jdk.7.x.x.tar.gz
    Now Setup class path.update-alternatives command is used set a symbolic link easily.
     
      sudo update-alternatives --install "/usr/bin/java" "java" "/opt/jdk1.7.0_05/bin/java" 20000
      sudo update-alternatives --install "/usr/bin/javac" "javac" "/opt/jdk1.7.0_05/bin/javac" 20000
      sudo update-alternatives --install "/usr/bin/javap" "javap" "/opt/jdk1.7.0_05/bin/javap" 20000
      sudo update-alternatives --install "/usr/bin/appletviewer" "appletviewer" "/opt/jdk1.7.0_05/bin/appletviewer" 20000 
      after executing following command check the java version using following command .
       $ java -version
         java version "1.7.0_05"
         Java(TM) SE Runtime Environment (build 1.7.0_05-b06)
         Java HotSpot(TM) Server VM (build 23.1-b03, mixed mode)


Firefox java plugin sudo update-alternatives --install "/usr/lib/mozilla/plugins/libjavaplugin.so" "libjavaplugin.so" "/opt/jdk1.7.0_05/jre/lib/i386/libnpjp2.so" 1
             restart Firefox And Type about:plugins in the Location bar to confirm that the Java Plugin is loaded. You can also click the Tools menu to confirm that Java Console is there.