Perhaps something like:

if type -p java; then
    echo found java executable in PATH
    _java=java
elif [[ -n "$JAVA_HOME" ]] && [[ -x "$JAVA_HOME/bin/java" ]];  then
    echo found java executable in JAVA_HOME     
    _java="$JAVA_HOME/bin/java"
else
    echo "no java"
fi

if [[ "$_java" ]]; then
    version=_java" -version 2>&1 | awk -F '"' '/version/ {print $2}')
    echo version "$version"
    if [[ "$version" > "1.5" ]]; then
        echo version is more than 1.5
    else         
        echo version is less than 1.5
    fi
fi

For the case you describe, you should use the where command coupled with checking the exit code (ERRORLEVEL) to see if the program exists and is in the path.

Example:

    @echo off
    where java 2>NUL
    if "%ERRORLEVEL%"=="0" (call :JavaFound) else (call :NoJava)
    goto :EOF

    ::::::::::::::::::::::::::::::::::::::::::::
    :JavaFound
    ::::::::::::::::::::::::::::::::::::::::::::
    Echo Java found.. checking version...
    goto :EOF

    ::::::::::::::::::::::::::::::::::::::::::::
    :NoJava
    ::::::::::::::::::::::::::::::::::::::::::::
    Echo Java not found, you need to install it.
    :: install java here?
    goto :EOF

This works for older "1.x.y" format as well as newer "x.y" format:

java -version 2>&1 \
  | head -1 \
  | cut -d'"' -f2 \
  | sed 's/^1\.//' \
  | cut -d'.' -f1

Source: https://odoepner.wordpress.com/2014/07/27/get-java-version-string-via-shell-commands/

When installing a public JRE (used by the Java plugin), a java.exe file is also created in C:\WINNT\system32 (IIRC). It's probably this java command that is executed, since C:\WINNT\system32 comes before the JDK/bin directory in your PATH.

Put the JDK/bin directory at the beginning of the PATH.

I was editing the wrong file(/etc/profile) all that time. Adding following lines to /etc/bashrc resolved the issue.

export JAVA_HOME="/usr/java/jdk1.8.0_172-amd64/"
export PATH=$JAVA_HOME/bin:$PATH

Thanks

Update : Please refer the comment by @jsbillings below. creating a custom script in /etc/profile.d/ and adding above lines is the most recommended.

It doesn't change value in path or java -version doesn't change in current instance of cmd

You have to restart cmd for the changes to take effect as a cmd shell inherits it environment from the parent process.

So what is the correct way to switch between Java versions from the command line?

Use a set of batch files, as follows:

Being a Java developer, I always compile and test my code on different Java versions. But switching between them is a huge problem. So finally I found an easy method to do this. You have to create following batch files and place them in directory you open your command line in or in SYSTEM PATH. You can use you favorite text editor to create these files.

jdk14.bat

@echo off
echo Setting JAVA_HOME
set JAVA_HOME=C:\j2sdk1.4.2_12
echo setting PATH
set PATH=C:\j2sdk1.4.2_12\bin;%PATH%
echo Display java version
java -version

jdk15.bat

@echo off
echo Setting JAVA_HOME
set JAVA_HOME=C:\Program Files\Java\jdk1.5.0_12
echo setting PATH
set PATH=C:\Program Files\Java\jdk1.5.0_12\bin;%PATH%
echo Display java version
java -version

jdk16.bat

@echo off
echo Setting JAVA_HOME
set JAVA_HOME=C:\Program Files\Java\jdk1.6.0_11
echo setting PATH
set PATH=C:\Program Files\Java\jdk1.6.0_11\bin;%PATH%
echo Display java version
java -version

Make sure you assign the appropriate JAVA_HOME value in batch files, according to your Java installation. Whenever you want to switch between Java versions, just run the respective batch file and you are done.

Note: JAVA_HOME and the path to java must always refer to the exact same version of the JDK. If you mix them up, unpredictable things will happen!

Source Switch between different JDK versions in Windows | Oracle Pranav's Blog

You need to add $JAVA_HOME/bin to your PATH

You can verify this easily:

$ PATH=$PATH:$JAVA_HOME/bin
$ java -version

After you've verified it works, edit your ~/.bashrc file to include the line

export PATH=$PATH:$JAVA_HOME/bin