Generic Implementation

Implement the generic IndexedList ADT with a concrete Java class.

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

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.

Define the fields with a generic type. Here we need a generic array.
```
private T[] data;
```
Initialize the fields in a constructor (instantiate when needed). We will leave this for the next lesson!
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.

Data Structures

Generic Implementation