If you mean 'tools.jar', since upper- and lower-case letters matter, it comes
with Java, not Linux as such.

Is Java installed on your Linux?

I have a JDK on my Redhat box in /usr/java/jdk1.6.0_01/,the location I
specified when I installed Java.

Within there is the directory /usr/java/jdk1.6.0_01/lib/, in which I find
/usr/java/jdk1.6.0_01/lib/tools.jar

When running with this version of Java, I have an environment variable
JDK_HOME set to the top of my JDK tree.  Let's say I have my main Java version
installed in /usr/java/java/ (which I do, through the magic of symlinks).

$ export JDK_HOME=/usr/java/java
$ ls ${JDK_HOME}/lib/

For a non "Java" related solution to finding files in Linux:

You can usually use the locate command:

locate -i tools.jar

Or, if that doesn't work, the brute force method:

find / -iname Tools.jar -print

You can use the "man" command to lookup what each of the above
commands does and what the options are.

- Kurt