Java Pass Method as Parameter

Question

I am looking for a way to pass a method by reference. I understand that Java does not pass methods as parameters, however, I would like to get an alternative.

I\'ve

Answer 1

I did not found any solution here that show how to pass method with parameters bound to it as a parameter of a method. Bellow is example of how you can pass a method with parameter values already bound to it.

1. Step 1: Create two interfaces one with return type, another without. Java has similar interfaces but they are of little practical use because they do not support Exception throwing.

    public interface Do {
    void run() throws Exception;
    }


    public interface Return {
        R run() throws Exception;
    }

2. Example of how we use both interfaces to wrap method call in transaction. Note that we pass method with actual parameters.

    //example - when passed method does not return any value
    public void tx(final Do func) throws Exception {
        connectionScope.beginTransaction();
        try {
            func.run();
            connectionScope.commit();
        } catch (Exception e) {
            connectionScope.rollback();
            throw e;
        } finally {
            connectionScope.close();
        }
    }

    //Invoke code above by 
    tx(() -> api.delete(6));

Another example shows how to pass a method that actually returns something

        public  R tx(final Return func) throws Exception {
    R r=null;
    connectionScope.beginTransaction();
    try {
                r=func.run();
                connectionScope.commit();
            } catch (Exception e) {
                connectionScope.rollback();
                throw e;
            } finally {
                connectionScope.close();
            }
        return r;
        }
        //Invoke code above by 
        Object x= tx(() -> api.get(id));