- Debugging is hard, knowing common mistakes can make it much easier to help students.
- Common errors include the following:
- Not naming a class the same as saved file name.
- Case sensitive typos.
- Using the number 1 versus the letter l. Especially in the Java print statement, System.out.println("Text Here");.
- Using a semicolon— ; —after a while statement.
- Putting a return type with constructors.
- Confusion regarding the order of operations.
- Messing up braces: using {} instead of [] or ().
- Putting parenthesis after the length method for Arrays in Java, it’s just .length without parenthesis.
- Students get really confused here because the Java method .size() for ArrayList has parentheses.
- With interface, students don’t realize you don’t need abstract in front of every method
- Confusion with implement versus extend, often saying "extend" when they mean implement.
- Confusion with super.method() and super(), the constructor call.
- This needs to be rote memorized, practiced, and reinforced frequently.
- Forgetting curly braces {} with loops.
- Out of bounds errors in loops. Looping to x+1 when students only need to loop to x-1.
- If you don’t minus one from the last element you want to look at you go out of bounds.
- Modulo, when students see modular arithmetic (e.g., 7%2) they cannot remember which number divides which.