How do I import jars into my java program?

Question

I've downloaded two jars. I want to import some of their contained classes. How do I do this?

It's for my algorithms class. I've tried following the instructions on the following site to no avail.

http://algs4.cs.princeton.edu/code/

There's an installer for OSX (I'm running Mountain Lion) which allegedly adds the jars to your classpath. Unfortunately it also installs Dr. Java. I'd rather just use Sublime and Terminal. I assumed it would be easy enough just...

import java.stdlib;

in my Percolation.java file, but javac-ing that program yields a "package stdlib does not exist", as does

import stdlib;

I've added the location of stdlib.jar and algs4.jar to my Terminal CLASSPATH manually via:

export CLASSPATH=$CLASSPATH:/Users/Michael/path/to/jar/algs4.jar:/Users/Michael/path/to/jar/algs4.jar
export CLASSPATH=$CLASSPATH:/Users/Michael/path/to/jar/stdlib.jar:/Users/Michael/path/to/jar/stdlib.jar

I've also attempted

javac -cp $CLASSPATH:/Users/Michael/path/to/jar/algs4.jar:/Users/Michael/path/to/jar/stdlib.jar Percolation.java

But I still get a

javac Percolation.java
Percolation.java:1: cannot find symbol
symbol  : class stdlib
location: package java
import java.stdlib;
       ^
Percolation.java:2: package java.algs4 does not exist
import java.algs4.WeightedQuickUnionUF;
             ^

What's going on here?

Also is there a way to permanently add those values to my CLASSPATH in OS X mountain lion. I have to perform that command with every new Terminal.

Answer 1

If you're using Terminal to compile and launch your program, then in the Terminal window, begin by setting the CLASSPATH:

$ export CLASSPATH=$CLASSPATH:/Users/Michael/path/to/jar1.jar:/Users/Michael/path/to/jar2.jar

Then you can type echo $CLASSPATH and see that the jars are referenced.

Now, in the same Terminal window, use javac to compile your class. Setting the CLASSPATH as above only applies to the current Terminal window and any processes launched from it.

Alternately you can pass the CLASSPATH to javac:

$ javac -cp $CLASSPATH:/Users/Michael/path/to/jar1.jar:/Users/Michael/path/to/jar2.jar MyClass.java

To persist this CLASSPATH for future Terminal sessions, add the export line above to the file .profile in your home directory.