AP2017.java

// Question 1
public class Digits {

    private ArrayList<Integer> digitList;

    // Alternative method: parse num as String, use charAt and Integer.parseInt to extract the digits
    public Digits(int num) {
        digitList = new ArrayList<Integer>();
        if (num == 0) digitList.add(0);
        while (num > 0) {
            digitList.add(0, num % 10);
            num /= 10;
        }
    }
  
    // Alternative method: use for loop indices for comparison
    public boolean isStrictlyIncreasing() {
        int lastDigit = -1;
        for (int digit : digitList) {
            if (digit <= lastDigit) return false;
            lastDigit = digit;
        }
        return true;
    }

}

// Question 2
public class MultPractice implements StudyPractice {

    private int c;
    private int x;

    public MultPractice(int c, int x) {
        this.c = c;
        this.x = x;
    }

    public String getProblem() {
        return c + " TIMES " + x;
    }

    public void nextProblem() {
        x++;
    }

}

// Question 3
public class Phrase {

    private String currentPhrase;

    public Phrase(String p) {
        currentPhrase = p;
    }

    public int findNthOccurrence(String str, int n) {
        /* Implementation not shown */
    }

    public void replaceNthOccurrence(String str, int n, String repl) {
        int index = findNthOccurrence(str, n);
        if (index == -1) return;
        currentPhrase = currentPhrase.substring(0, index) + repl + currentPhrase.substring(index + str.length());
    }

    // Alternative method (-1 mark penalty due to findNthOccurrence not being utilized):
    // start from the end of string, loop backwards, substring in each loop
    public int findLastOccurrence(String str) {
        int n = 0, lastIndex = -1;
        while (true) {
            n++;
            int index = findNthOccurrence(str, n);
            if (index == -1) break;
            lastIndex = index;
        }
        return lastIndex;
    }

    public String toString() {
        return currentPhrase;
    }

}

// Question 4
public class Successors {

    public static Position findPosition(int num, int[][] intArr) {
        for (int r = 0; r < intArr.length; r++) {
            for (int c = 0; c < intArr[0].length; c++) {
                if (intArr[r][c] == num) return new Position(r, c);
            }
        }
        return null;
    }

    public static Position[][] getSuccessorArray(int[][] intArr) {
        Position[][] successorArr = new Position[intArr.length][intArr[0].length];
        for (int r = 0; r < intArr.length; r++) {
            for (int c = 0; c < intArr[0].length; c++) {
                successorArr[r][c] = findPosition(intArr[r][c] + 1, intArr);
            }
        }
        return successorArr;
    }

}

Thanks!