Question

Here is the indexOf method that I wrote:

public static int indexOf(char[] arr, char ch) {
           if(arr == null || arr.length == 0) {
               return -1;
           }
           for (int i = 0; i < arr.length; i++) {
               if(arr[i] == ch) {
                   return i;
               }
           }
       return -1;
       }

Now I have to write this method:

import java.util.Arrays;
       import java.util.Random;
       import java.util.Scanner;

       * TODO Write a summary of the role of this class in the
       * MasterMind program.
  
       public class MasterMind {

/**
       * Checks whether the code is the correct length and only contains valid symbols.
       * Uses the indexOf method you wrote to check whether each character in the input is in the
       * symbols array. If code or symbols are null then false is returned.

       * For all arrays, don't assume a length but use the array .length attribute.
       *   
       * @param numPositions The required number of symbols in the code.
       * @param symbols The allowed symbols in the code.
       * @param code The code that is being checked.
       * @return true if the code is the correct length and has only valid symbols otherwise
       * returns false.
       */
       public static boolean isValidCode( int numPositions, char [] symbols, char [] code) {
       return false; //TODO replace
       }

Answer 1

// TODO file header

import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;

/**
 * TODO Write a summary of the role of this class in the
 * MasterMind program.
 *
 * @author TODO add your name here
 */
public class MasterMind {
    /**
     * Returns the index within arr of the first occurrence of the specified character.
     * If arr is null or 0 length then return -1. For all arrays, don't assume a length
     * but use the array .length attribute.
     *
     * @param arr The array to look through.
     * @param ch  The character to look for.
     * @return The index within the array of the first occurrence of the specified
     * character or -1 if the character is not found in the array.
     */
    public static int indexOf(char[] arr, char ch) {
        if (arr == null || arr.length == 0) {
            return -1;
        }
        for (int i = 0; i < arr.length; i++) {
            if (arr[i] == ch) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Checks whether the code is the correct length and only contains valid symbols.
     * Uses the indexOf method you wrote to check whether each character in the input is in the
     * symbols array. If code or symbols are null then false is returned.

     * For all arrays, don't assume a length but use the array .length attribute.
     *
     * @param numPositions The required number of symbols in the code.
     * @param symbols The allowed symbols in the code.
     * @param code The code that is being checked.
     * @return true if the code is the correct length and has only valid symbols otherwise
     * returns false.
     */
    public static boolean isValidCode( int numPositions, char [] symbols, char [] code) {
        for (int i = 0; i < code.length; i++) {
            if (indexOf(symbols, code[i]) == -1) {
                return false;
            }
        }
        return true;
    }
}