Question 12.1: Write constructors for the classes SportsShoe and Runner below, by looking at the main function to see how many arguments each constructor has.
class SportsShoe begin property String model; // what kind of shoe it is property double speedBoost; // the boosting factor of the shoe // constructor goes here: // Useful method for debugging method String toString() begin return "I am a shoe called " + model + " and my boosting factor is " + speedBoost; end end class Runner begin private property String name; // Runner's name. private property int speed; // speed of runner in km/hr. private property SportsShoe shoes; // which shoe they are wearing // constructor goes here: // Useful method for debugging method String toString() begin return "I am a runner and my name is " + name + " and my shoes are " + shoes; end /** *** This private method computeSpeed works out the runners speed, *** based on their basic speed and the speed boost due to the *** SportsShoe that they are currently wearing. */ // method goes here: /** ** Prints the result of racing two runners against each other. */ function void race(Runner r1, Runner r2) begin if (r1.computeSpeed()>r2.computeSpeed()) then begin System.out.println("Runner " + r1.name + " beats " + r2.name); end else begin System.out.println("Runner " + r2.name + " beats " + r1.name); end end /** ** Swaps the shoes of two runners. */ function void swapShoes(Runner r1, Runner r2) begin var SportsShoe tempShoe = r1.shoes; r1.shoes = r2.shoes; r2.shoes = tempShoe; end end class RunnerTest begin beginMain var SportsShoe nike = new SportsShoe("Nike NX-71", 2.0); var SportsShoe reebock = new SportsShoe("Reebock R20", 2.3); var SportsShoe puma = new SportsShoe("Puma P200-MMX",4.8); var Runner sg = new Runner("Speedy Gonzalez", 55, nike); var Runner sw = new Runner("Slick Willy", 49, reebock); var Runner fa = new Runner("Fat Albert", 15, puma); Runner.race(sg,sw); // Runner.race(sg,sw,fa); // sg.raceAgainst(sw); endMain end
Question 12.2: In the Runner class, write the private method computeSpeed that has no arguments and returns a double-precision floating point value that equals the runner's running speed. Note that the speed of a runner is determined by multiplying their speed property with the speedBoost property of the shoes that they are wearing. For example, Speedy Gonzalez's running speed = 55 * 2.0 = 110.0.
Question 12.3: Fix the race method so that it checks for a draw.
Question 12.4: By copying the race method, write a three-parameter race method for racing three runners against each other. Two methods in the same class with the same name is called overloading in Java. Add a call to this method from the main function.
Question 12.5: What is the difference between a method and a function? Write a one parameter method raceAgainst that behaves exactly like two-parameter function race. There are two ways of doing this, one is to optionally use the this keyword rather than one of the parameters r1 or r2. The second way is for race to simply call race using this as one of the arguments to the function.
Question 12.6: Is it true that any method can be re-worked into a function and vice versa?
Question 12.7: The swapShoes method in the Runner class swaps the shoes of two runners. Add some code to the main function to swap the shoes of two runners and verify that the shoes do indeed get swapped.
Question 12.8: Write a method called swapNames that swaps the names of two runners. You can put this function into any class but it makes the most sense to put it into the Runner class since it has two Runner parameters.
Question 12.9: Write a method swapSpeeds that swaps the speed properties of two runners.
|Back to J.T.W|
This page has the following hit count: