I'm not sure that this is the appropriate place for this question; if it is not, could someone direct me please?

I have been trying to run the following (from "Groovy in Action")
/**
 *
 */

/**
 * @author syssdc
 *
 */
class Money {
    private int amount
    private String currency
   
    Money (amountValue, currencyValue) {
        amount = amountValue
        currency = currencyValue
    }
   
    // Overide "=="
    boolean equals (Object other) {
        if (null == other)                return false
        if (! (other instanceof Money))    return false
        if (currency != other.currency)    return false
        if (amount != other.amount)        return false
        return true
    }
   
    int hashCode() {
        amount.hashCode() + currency.hashCode()
    }
   
    // Implement "+" operator
    Money plus (Money other) {
        if (null == other) return null;
        if (other.currency != currency) {
            throw new IllegalArgumentException (
                    "cannot add $other.currency to $currency")
        }
        return new Money(amount + other.amount, currency)
    }
}

def buck = new Money(1, 'USD')
assert buck
assert buck == new Money(1, 'USD')
assert buck + buck == new Money(2, 'USD')

It runs fine in the Groovy Console, throws the following from Eclipse when I do "compile groovy" from the File menu:
java.lang.NoClassDefFoundError: org/apache/tools/ant/taskdefs/Java
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$000(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)
Caused by: java.lang.ClassNotFoundException: org.apache.tools.ant.taskdefs.Java
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)
        ... 12 more
Exception in thread "main"

It is entirely possible that I have gotten my Build setup screwed up.

I also get the following error, repeatedly, in a popup dialog:

'Compute launch button tooltip' has encountered a problem.  An internal error occurred during 'Compute launch button tooltip'.

The details button yields the following: java.lang.NullPointerException

I am running the latest Eclipse (Version: 3.4.2 Build id: M20090211-1700)  and Groovy Plug-in (1.5.7.20081120_2330)

Any help will be greatly appreciated.
Susan