7.9. Additional Practice

Question 1

Refer to the UML diagram below. Write a static method named listCarnivores that takes an array of Animal objects and returns an String[] containing the names of all animals whose diet is “Carnivore”.

hide circle set namespaceSeparator none skinparam classAttributeIconSize 0 package "cs1302.example" { Driver -up-> Animal: uses class Animal { -name: String -genus: String -diet: String +<<new>> Animal(name: String, genus: String, diet: String) +getName(): String +getDiet(): String +getGenus(): String } class Driver { {static} +main(args: String[]): void } hide Driver fields }

Method header to complete:

/**
 * Returns an array of the names of all carnivorous animals
 * in the given array.
 *
 * @param animals an array of Animal objects
 * @return a {@code String[]} containing the names of the carnivores
 */
public static String[] listCarnivores(Animal[] animals) {
    // your code here
} // listCarnivores
Solution
 1/**
 2 * Returns an array of the names of all carnivorous animals
 3 * in the given array. Null arrays and null entries are ignored.
 4 *
 5 * @param animals an array of {@code Animal} objects
 6 * @return a {@code String[]} containing the names of the carnivores
 7 */
 8public static String[] listCarnivores(Animal[] animals) {
 9
10      if (animals == null) {
11         return new String[0];
12      }
13
14      // First, count the number of carnivores
15      int count = 0;
16      for (Animal individual : animals) {
17         if (individual != null && individual.getDiet().equals("Carnivore")) {
18            count++;
19         } // if
20      } // for
21
22      // Create array of correct size
23      String[] carnivores = new String[count];
24
25      // Fill the array
26      int index = 0;
27      for (Animal individual : animals) {
28         if (individual != null && "Carnivore".equals(individual.getDiet())) {
29            carnivores[index] = individual.getName();
30            index++;
31         } // if
32      } // for
33
34      return carnivores;
35} // listCarnivores
Question 2

Refer to the UML diagram below. Write a static method named countByGenus that takes an array of Animal objects and a String representing a genus, and returns the number of animals in the array that belong to that genus.

hide circle set namespaceSeparator none skinparam classAttributeIconSize 0 package "cs1302.example" { Driver -up-> Animal: uses class Animal { -name: String -genus: String -diet: String +<<new>> Animal(name: String, genus: String, diet: String) +getName(): String +getDiet(): String +getGenus(): String } class Driver { {static} +main(args: String[]): void } hide Driver fields }

Method header to complete:

/**
 * Counts the number of animals in the given array that belong
 * to the specified genus. Null arrays, null genus, or null
 * entries in the array are ignored.
 *
 * @param animals an array of {@code Animal} objects
 * @param genus   the genus to count
 * @return the number of animals matching the specified genus
 */
public static int countByGenus(Animal[] animals, String genus) {
    // your code here
} // countByGenus
Solution
 1/**
 2  * Counts the number of animals in the given array that belong
 3  * to the specified genus. Null arrays, null genus, or null
 4  * entries in the array are ignored.
 5  *
 6  * @param animals an array of {@code Animal} objects
 7  * @param genus   the genus to count
 8  * @return the number of animals matching the specified genus
 9  */
10 public static int countByGenus(Animal[] animals, String genus) {
11
12     int count = 0;
13
14     if (animals == null || genus == null) {
15         return 0;
16     } // if
17
18     for (Animal individual : animals) {
19         if (individual != null && genus.equals(individual.getGenus())) {
20             count++;
21         } // if
22     } // for
23
24     return count;
25
26 } // countByGenus