Functional Java

package swensen.functional;

import java.util.concurrent.Callable;

/**
 * Provides compatibility between Func0 and Callable.
 * @author Stephen Swensen
 * @param <T> the functor return type.
 */
public abstract class CallableFunc<T> implements Func0<T>, Callable<T> {
    /**
     * Create a CallableFunc from a Func0.
     * @param <T> the functor return type.
     * @param func the Func0 to wrap, not null.
     * @return a new CallableFunc.
     */
    public static <T> CallableFunc<T> from(final Func0<? extends T> func)
    {
        if(func == null)
            throw new NullPointerException("func");

        return new CallableFunc<T>() {
            public T call() {
                return func.call();
            }
        };
    }

    /**
     * Create a CallabeFunc from a Callable. If callable throws an Exception, it is caught and rethrown wrapped as a RuntimeException.
     * @param <T> the functor return type.
     * @param callable the Callable to wrap, not null.
     * @return a new CallableFunc.
     */
    public static <T> CallableFunc<T> from(final Callable<? extends T> callable)
    {
        if(callable == null)
            throw new NullPointerException("callable");

        return new CallableFunc<T>() {
            public T call() {
                try {
                    return callable.call();
                }
                catch (Exception e){
                    throw new RuntimeException(e);
                }
            }
        };
    }
}