Error: JAVA_HOME is not defined correctly.

[David Gonzalez Rivera]

Is there a way to set the JAVA_HOME?
I have JRE installed (and JDK too)

I'm trying to compile jEdit (Yes I know I can download the deb, but I 
feeling a bit bored so I prefer learning a bit more :) )

Since I need this app, it tells me this

david at akulinux:~/Files/apache-ant-1.6.5$ ./build.sh
Warning: JAVA_HOME environment variable not set.
  If build fails because sun.* classes could not be found
  you will need to set the JAVA_HOME environment variable
  to the installation directory of java.
Error: JAVA_HOME is not defined correctly.
  We cannot execute java
Bootstrap FAILED
david at akulinux:~/Files/apache-ant-1.6.5$