Ubuntu – How to get ORACLE JAVA SE 7 to work

I am a newbie to Ubuntu, so kindly be considerate.

I recently manually downloaded & installed (Java SE 7ux) JavaSE 1.7.0_51.
Linux x64 (for 64-bit system) "tar.gz" package.
My Ubuntu version is 13.10 (OS 64 bit)

I carefully following the instructions from: How to Install JDK 7 on Ubuntu

To verify that the installation was successful I wrote:

javac -version

and get the below results:

Error occurred during initialization of VM
java/lang/NoClassDefFoundError: java/lang/Object

$ which java gives the below results:  
/usr/bin/java

$ which javac also gives the below results:
/usr/bin/javac

I repeated the steps a couple of times just in case I missed out an important step but still got the same results. After a couple of researching on-line I found out @ Reference, that I could actually install Java on Ubuntu via PPA repository.

After the installation when I

$ java -version 

I still get:

Error occurred during initialization of VM
java/lang/NoClassDefFoundError: java/lang/Object

However when I

$ cd /usr/bin
$ ls -ld java*

I get:

lrwxrwxrwx 1 root root 22 Feb 19 19:06 java -> /etc/alternatives/java
lrwxrwxrwx 1 root root 23 Feb 17 02:15 javac -> /etc/alternatives/javac
lrwxrwxrwx 1 root root 25 Feb 19 20:09 javadoc -> /etc/alternatives/javadoc
lrwxrwxrwx 1 root root 32 Feb 19 20:09 javafxpackager -> /etc/alternatives/javafxpackager
lrwxrwxrwx 1 root root 23 Feb 19 20:09 javah -> /etc/alternatives/javah
lrwxrwxrwx 1 root root 23 Feb 19 20:09 javap -> /etc/alternatives/javap
lrwxrwxrwx 1 root root 25 Feb 19 20:09 java_vm -> /etc/alternatives/java_vm
lrwxrwxrwx 1 root root 24 Feb 17 02:15 javaws -> /etc/alternatives/javaws

Also similar to:

$ cd /etc/alternatives 
$ ls -ld java*

lrwxrwxrwx 1 root root 36 Feb 19 19:15 java -> /usr/local/java/jdk1.7.0_51/bin/java
lrwxrwxrwx 1 root root 37 Feb 17 02:15 javac -> /usr/local/java/jdk1.7.0_51/bin/javac
lrwxrwxrwx 1 root root 38 Feb 19 20:09 javadoc -> /usr/lib/jvm/java-7-oracle/bin/javadoc
lrwxrwxrwx 1 root root 48 Feb 19 20:09 javadoc.1.gz -> /usr/lib/jvm/java-7-oracle/man/man1/javadoc.1.gz
lrwxrwxrwx 1 root root 45 Feb 19 20:09 javafxpackager -> /usr/lib/jvm/java-7-oracle/bin/javafxpackager
lrwxrwxrwx 1 root root 55 Feb 19 20:09 javafxpackager.1.gz -> /usr/lib/jvm/java-7-oracle/man/man1/javafxpackager.1.gz
lrwxrwxrwx 1 root root 36 Feb 19 20:09 javah -> /usr/lib/jvm/java-7-oracle/bin/javah
lrwxrwxrwx 1 root root 46 Feb 19 20:09 javah.1.gz -> /usr/lib/jvm/java-7-oracle/man/man1/javah.1.gz
lrwxrwxrwx 1 root root 36 Feb 19 20:09 javap -> /usr/lib/jvm/java-7-oracle/bin/javap
lrwxrwxrwx 1 root root 46 Feb 19 20:09 javap.1.gz -> /usr/lib/jvm/java-7-oracle/man/man1/javap.1.gz
lrwxrwxrwx 1 root root 42 Feb 19 20:09 java_vm -> /usr/lib/jvm/java-7-oracle/jre/bin/java_vm
lrwxrwxrwx 1 root root 42 Feb 17 02:15 javaws -> /usr/local/java/jdk1.7.0_51/jre/bin/javaws

Note that

javadoc.1.gz -> /usr/lib/jvm/java-7-oracle/man/man1/javadoc.1.gz
javafxpackager.1.gz -> /usr/lib/jvm/java-7-oracle/man/man1/javafxpackager.1.gz
javah.1.gz -> /usr/lib/jvm/java-7-oracle/man/man1/javah.1.gz
javah.1.gz -> /usr/lib/jvm/java-7-oracle/man/man1/javah.1.gz

…are all in RED

• What does all this mean and most importantly how do I make my Java installation work?

Looking forward to you help!