Ant and Classpath

Question

I just started to learn Java using Thinking in Java book, and have some troubles using ant.

I'm using Ubuntu 12.04, and have openjdk 7 java installed. I also setup the CLASSPATH to be the code folder

When I run ant in code folder, this is the output:

Exception in thread "main" java.lang.RuntimeException: JDK 1.4.1 or higher is required to run the examples in this book.
[CheckVersion]  at com.bruceeckel.tools.CheckVersion.main(Unknown Source)

However when I run java -version, this is the output:

java version "1.6.0_27"
OpenJDK Runtime Environment (IcedTea6 1.12.5) (6b27-1.12.5-0ubuntu0.12.04.1)
OpenJDK 64-Bit Server VM (build 20.0-b12, mixed mode)

How to setup ant and classpath correctly?

P/S: Thanks everyone for the help!!! I figured out why it fails to check the version. The testing condition is "if(minor < '4' || point < '1')" in CheckVersion.java. Yet my version is 1.6.024, eventhough 6>4 but 0<1 that's why it failed. I guess we need to rewrite the testing condition!

Answer 1

Try setting your JAVA_HOME environment variable to the install directory of your 1.6 JDK.

When you type "java -version", the command shell is using the first java executable it finds in your PATH. Ant probably looks for the java executable in the "bin" sub-directory of your JAVA_HOME directory.

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To find the location of your java executable, type the following:

which java

and let's say you got the following output:

/usr/local/java1.6/bin/java

You would then set your JAVA_HOME variable to /usr/local/java1.6. Assuming a Bourne or Bash shell, the syntax for that would be

export JAVA_HOME=/usr/local/java1.6