Save this script and run , you will see this screen:

Choose the first option and past the path for your jdk folder:

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#!/bin/bash
### BEGIN INIT INFO
# SCRIPT TO SET JAVA_HOME ON LINUX
### END INIT INFO</code>
# Author: Samuel Teixeira samuelteixeiras[at]gmail.com
 
 
 
    next=menu
 
    # loop principal
    while : ; do
 
        
        case "$next" in
              
        menu)
            resposta=$(
              dialog --stdout               \
              --title 'Menu'  \
              --menu  'Select one option:' \
              0 0 0                   \
              1 'Set Java Path.'\
              0 'Exit'                )
 
                # CANCELAR or ESC, exir...
                [ $? -ne 0 ] && break
 
                # De acordo com a opção escolhida, dispara programas
                case "$resposta" in
             
                1)
                next=setPath
                back=menu
                ;;
             
                0) break ;;
                esac
                ;;
 
         
 
 
 
            setPath)
            next=$back
            dir=$(dialog           --stdout            \
               --title 'Set java Path'                         \
               --inputbox 'Please, Insert the name of java path \n Ex: /usr/local/jdk1.8.0:'  \
            0 0)
         
            bashFile=~/.bashrc
         
            if [ -d "$dir" ]
            then
                echo "export JAVA_HOME=$dir" >> $bashFile
                echo "export PATH=$PATH:$dir/bin" >> $bashFile
 
            else
                echo "$dir not found."
            fi
 
            source $bashFile
             
            sudo update-alternatives --install "/usr/bin/java" "java" "$dir/bin/java" 1
            sudo update-alternatives --install "/usr/bin/javac" "javac" "$dir/bin/javac" 1
            sudo update-alternatives --install "/usr/bin/javaws" "javaws" "$dir/bin/javaws" 1
            sudo chmod a+x /usr/bin/java
            sudo chmod a+x /usr/bin/javac
            sudo chmod a+x /usr/bin/javaws
            sudo chown -R root:root $dir
 
            break
 
            ;;
         
 
         
        *)
            echo "Bad Window '$next'."
            echo Abort programm...
            exit
        esac
 
        # Aqui é feito o tratamento genérico de Código de Retorno
        # de todas as telas. Volta para a tela back se for
        # CANCELAR, sai do programa se for ESC.
        retorno=$?
        [ $retorno -eq 1   ] && next=$back      # cancel
        [ $retorno -eq 255 ] && break               # Esc
 
    done
    clear
    sudo update-alternatives --config java
    java -version