# RandomStringChooser - Part B

Each coding exercise has its own folder. Open its `.java` file and press **Run** to try it. **Run Tests** checks every graded exercise in this lesson at once.

**Part b.** The following partially completed `RandomLetterChooser` class is a subclass of the `RandomStringChooser` class. You will write the constructor for the `RandomLetterChooser` class.

```java
public class RandomLetterChooser extends RandomStringChooser
{
    /** Constructs a random letter chooser using the given string str.
     *  Precondition: str contains only letters.
     */
    public RandomLetterChooser (String str)
    { /* to be implemented in part (b) */ }

    /** Returns an array of single-letter strings.
     *  Each of these strings consists of a single letter from str.  Element k
     *  of the returned array contains the single letter at position k of str.
     *  For example, getSingleLetters("cat") return the
     *  array {"c", "a", "t" }.
     */
    public static String[] getSingleLetters(String str)
    {    /* implementation not shown */ }
```

The following code segment shows an example of using `RandomLetterChooser`.

```java
RandomLetterChooser letterChooser = new RandomLetterChooser("cat");
for (int k = 0; k < 4; k++)
{
    System.out.print(letterChooser.getNext());
}
```

The code segment will print the three letters in `"cat"` in one of the possible orders. Because there are only three letters in the original string, the code segment prints `"NONE"` the fourth time through the loop. One posible output is shown below.

```
actNONE
```

Assume that the `RandomStringChooser` class that you wrote in part (a) has been implemented correctly and that `getSingleLetters` works as specified. You must use `getSingleLetters` appropriately to receive full credit.

Complete the `RandomLetterChooser` constructor below. The following code block shows the construtor declaration.

```java
/** Constructs a random letter chooser using the given string str.
 *  Precondition: str contains only letters.
 */
public RandomLetterChooser(String str)
```

## Try and Solve It

Complete the `RandomLetterChooser` constructor below Copy in your RandomStringChooser class from the previous lesson (delete the public from in front of it since there can only be 1 public class if you have more than one).

The code below has a main method for testing. Write the constructor for the `RandomLetterChooser` class and use the main method to test it.

### Exercise 1

Complete the `RandomLetterChooser` constructor below (which can be 1 line of code). Copy in your RandomStringChooser class from the previous lesson (delete the public from in front of it since there can only be 1 public class if you have more than one).

> Open the `01-RandomStrChooserB1` folder and edit `RandomLetterChooser.java`. Press **Run** to try it; **Run Tests** checks it (2 tests).