RandomStringChooser - Part B - 2nd time¶

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

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.

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 possible 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.

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

Try and Solve It - Again¶

Complete the RandomLetterChooser constructor below.

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

import java.util.List;
import java.util.ArrayList;

public class RandomLetterChooser extends RandomStringChooser
{
    /** Constructs a random letter chooser using the given string str.
     *  Precondition: str contains only letters.
     */
    public RandomLetterChooser (String str)
    {
      //*** write the constructor here ***!
    }

/** 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)
    {
       String[] strArr = new String[str.length()];
       for (int i = 0; i < str.length(); i++)
       {
          strArr[i] = str.substring(i, i+1);
       }
       return strArr;
    }

public static void main(String[] args)
    {
        RandomLetterChooser letterChooser = new RandomLetterChooser("cat");
        System.out.println("This should print three letters at random from cat and then NONE");
        for (int k = 0; k < 4; k++)
        {
            System.out.print(letterChooser.getNext());
        }
     }
}

class RandomStringChooser
{
    /* field */
    private List<String> words;

/* constructor */
    public RandomStringChooser(String[] wordArray)
    {
        words = new ArrayList<String>();

for (String singleWord : wordArray)
        {
            words.add(singleWord);
        }
    }

/* getNext method */
    public String getNext()
    {
        int pos = 0;

if (words.size() > 0)
        {
            pos = (int) (Math.random() * words.size());

return words.remove(pos);
        }
        return "NONE";
     }
}

You have attempted of activities on this page