Activity 3.2 - Using the CarTracker class

Topic

In this activity we make use of the methods defined in the class CarTracker.

Materials

In addition to the Solution document, the project for this activity contains the classes:

• CarTracker;
• TreasureHunt, which needs appropriate statements adding to it;
• TreasureHunt_Solution, our sample answer.

Task

Your task is to locate a 'treasure' hidden somewhere on a grid system. The CarTracker class discussed in Unit 3 operates with a grid system, and so we can use CarTracker objects to help us determine where the treasure is by making use of information supplied about the location of the treasure.

You are given the following information.

• All distances are in straight lines and measured in kilometres.
• The treasure is located at either Point A, position (11, 5) or at Point B, position (1, 9).
• Spyglass Hill is at grid position (8, 33).
• Smuggler's Cove is at grid position (6, 18).
• Parrot Point is at grid position (15, 25).
• The treasure is more than 5 km from Spyglass Hill, more than 10 km from Parrot Point and not more than 11 km from Smuggler's Cove.

1. Decide whether the treasure lies at A or B, based on distances between points A and B and Spyglass Hill, Smuggler's Cove and Parrot Point.
2. How far would you travel if you started from Spyglass Hill, went first to the treasure, then journeyed on to the Ship Inn at (15,15)?

Instructions

Open the class TreasureHunt. Insert statements in the main method that will make the comparisons necessary to locate the site of the treasure, and work out the journey distance from Spyglass Hill to the Ship Inn via the treasure.

For example, we can construct a CarTracker object whose starting position is point A (11,5) and whose ending position is at SpyglassHill (8, 33) as follows:

CarTracker aToSpyglass = new CarTracker(11,5,8,33);

Then the expression aToSpyglass.greaterThan(5) tells if the distance from A to Spyglass Hill is more than 5km. This is one thing that must be true if A is where the treasure is. There are two other things that must be true.

We can perform the same tests for B's position.

See our TreasureHunt_Solution for one way to solve the problem.