com1101 Lab 8

Part 1 Iterating With For Loops

In this lab we will use the IRange interface to iterate over collections.

Open the IRangeTest.java file and study the code for the methods containsBlueEyedPerson and allOverEighteen.

1. IRangeTest.java contains several definitions of data structures to help speed up testing. Add a few more definitions of your own.

2. Design the method containsPersonWithEyecolor which consumes an IRange collection and a Color object and determines if there is a Person in the collection with that eyecolor.

3. Design the method allOlderThan which consumes an IRange collection and a number of years and determines whether all the Persons in the collection are older than the given age.

4. Rewrite containsBlueEyedPerson and allOverEighteen to use
   containsPersonWithEyecolor and allOlderThan as helper functions. Reuse the tests!

Part 2 Writing andMap and orMap

We can write versions of the andMap and orMap methods that will work with IRange collections.

1. Open the file IPerson2Bool.java and study the IPerson2Bool interface. Write a class that implements IPerson2Bool and can be used to determine whether a person has blue eyes. Also write a class that implements IPerson2Bool and can be used to determine whether a Person is over 18 year old.

2. The header for andMap can be found in IRangeTests.java. Write andMap, which consumes an IPerson2Bool object and an IRange collection and determines if all of the Persons in the collection satisfy the IPerson2Bool object.

3. The header for orMap can be found in IRangeTests.java. Write orMap, which determines whether at least one Person in a IRange collection satisfies an IPerson2Bool object.

4. Rewrite containsBlueEyedPerson and allOverEighteen to use orMap and andMap. Use the classes from step 1. Reuse tests!

5. Create examples that use andMap and orMap with anonymous inner classes.

Part 3 Using the IRange Interface in a Recursion

Here is an example of a function, totalYears that sums up the ages of all the Persons in a collection. In the function I use an extra pair of {'s to introduce a local variable newTotal. Why must I use the local variable?

    // totalYears
    // To sum up all the ages of the People in the given IRangeCollection
    int totalYears(IRange i, int total) {
        if (i.hasMore()) {
            {
                int newTotal = total + ((Person)i.current()).age;
                i.next();
                return totalYears(i, newTotal);
            }
        }
        else
            return total;           
    }

1. Design listPersons which creates a AListPerson object using all the Persons in an IRange collection.

2. How about sort?

3. Can you rewrite these methods using a for loop?