learn-co-curriculum / java-mod-2-generics-lab

Generics Lab

Learning Goals

• Create and work with static generic methods.

Introduction

You'll be solving two problems to understand generics better. There are starter code samples in this lab's repository.

Problem 1: Convert generic array to String array

Declare a static method called convertToString in the GenericPractice class that accepts a generic array and returns the elements of the input array as a String.

Problem 2: Return the first element of a generic array

Building on the same foundation as the previous problem, in the same GenericPractice class, declare a static method called getFirstElement that accepts a generic array and returns the first element of the input array or null if the array is empty.

Sample Code

Consider the following sample code to help get you started and the driver class to test your code on both of the problems above:

public class GenericPractice {

    // Write the method convertToStringArray here

    // Write the method getFirstElement here
}

public class GenericDriver {
  public static void main(String[] args) {
    Integer[] inputInt = { 1, 2, 3 };
    Integer[] inputEmpty = new Integer[5];
    String[] inputStr = { "Cake", "Donut", "Cupcake" };

     System.out.println(GenericPractice.convertToStringArray(inputInt)); // [1, 2, 3]
     System.out.println(GenericPractice.convertToStringArray(inputStr)); // [Cake, Donut, Cupcake]

     System.out.println(GenericPractice.getFirstElement(inputInt)); // 1
     System.out.println(GenericPractice.getFirstElement(inputEmpty)); // null
     System.out.println(GenericPractice.getFirstElement(inputStr)); // Cake
  }
}

Sample Output

The driver class should produce the following output if the methods were written correctly:

[1, 2, 3]
[Cake, Donut, Cupcake]
1
null
Cake