Here's a sample of some of the features you'll find in Rephactor topics.

download or run
public class HelloWorld
    public static void main(String[] args)
        System.out.println("Hello, World!");
Run & Revise


interactive elements

Try This:  Color Objects and RGB Values

Adjust the sliders below to see how the RGB values relate to the color:


Color myColor = new Color(183, 44, 150);


Watch This:  Binary Search

quick check
What's this?

Quick Check Scoring

You can answer questions multiple times. Incorrect answers are tracked. For example:

3/6means 3 out of 6 questions in this Quick Check are currently correct
2is the total number of incorrect answers given in this Quick Check

Quick Check

Drag each term to the most appropriate description.

  • syntax error
  • debugging
  • program specification
  • runtime error
  • semantics
  • testing
  • natural language
  • syntax
  • logic error
967The meaning of a language element.
766The process of evaluating a program to discover errors.
940The process of determining the root cause of a problem and fixing it.
1627Used when humans communicate with each other.
679Determines how words and symbols are combined.
1265A problem such as omitting a necessary semicolon.
2169The set of requirements that must be satisfied by a program.
1358A problem such as dividing by zero.
1112A problem such as computing the wrong answer.

common error
API link
key concept
by the way