Generic Implementation

We must also update the implementation of the ArrayIndexedList since the IndexedList ADT uses generics.

1. Update the class declaration, parameters, and return types.

   public class ArrayIndexedList<T> implements IndexedList<T> {
   
     @Override
     public void put(int index, T value) {
       // stub
     }
   
     @Override
     public T get(int index) {
       return null; // stub
     }
   
     @Override
     public int length() {
       return 0; // stub
     }
   }
   

   Notice the <T> follows class name and interface name.

2. Define the fields with a generic type. Here we need a generic array.

   private T[] data;
   

3. Initialize the fields in a constructor (instantiate when needed). We will leave this for the next lesson!

4. Implement the methods.

   Here are implementation for get and length

   @Override
   public T get(int index) {
     return data[index];
   }
   
   @Override
   public int length() {
     return data.length;
   }
   

   Exercise Implement put.

   Solution

   @Override
   public void put(int index, T value) {
     data[index] = value;
   }
   

   Notice the implementation of get, length and put are identical to before using generics. This is the beauty of it: using generics in most cases requires very little change to your code.