Activity 2.5 - Using arrays

Topic

This activity is about array access.

Materials

In addition to the discussion of the solution in the Solution document, the project for this activity contains two classes:

• Ex2_5, for which you need to supply additional code;
• Main, which is run to test the code.

Tasks

It is common to list the planets of the Solar System in order of their distance from the Sun. However, many people have trouble remembering how the order goes. The method selectAPlanet was supposed to help with this, but unfortunately the programmer left out some segments of code:

• The check that the user submits a sensible planet number is incomplete;
• The code to print a planet's name was omitted;
• Pluto was omitted from the list of planets. (Pluto isn't considered to be a planet.)

The existing method runs but does not produce correct output. Your job is to supply the missing code.

Instructions

1. Run the project. You should find it prompts for a planet number. At this point you need to type a number in the window at the bottom of the NetBeans window and press Enter. The code should then print a planet name, but does not.
2. Open the class Ex2_5 and type in code missing from the method selectAPlanet at the two places indicated by comments. Don't forget that in Java the index of an array starts at 0, not 1. Re-run the project to check planet names are correctly printed.
3. Now modify the method to add "Pluto" to the array planets. If you have made the other changes in the right way, the program should still run properly, without further modification. Confirm this by executing the revised version.

Notes

This project makes use of the utility class Scanner to perform keyboard input. This class is discussed in Unit 4.