CHC4010 DevOps Week 4 – Practical: Debugging

Exercise 1: A Hello World Program in Java

Create a new project in IntelliJ. Write a simple program that prints “Hello world” and run it. This exercise is just to get you used to starting up and using IntelliJ.

Exercise 2: Fix an implementation of validMountainArray algorithm

Last week, we have tested this implementation of validMountainArray in Python. Here is the same implementation in Java:

static boolean isValidMountainArray(int[] arr) {
    int i = 1;
    boolean ascending = true;
    while (ascending && i < arr.length) {
        ascending = arr[i] > arr[i - 1];
        i++;
    }
    if (i == arr.length) return false;
    boolean descending = true;
    while (descending && i < arr.length) {
        descending = arr[i] < arr[i - 1];
        i++;
    }
    return i == arr.length;
}

Unzip starting_files.zip and move the file ValidMountainArray.java into the src folder of your IntelliJ project. Extra points if you could do it with CLI!

Enable assertions and run the file. Based on the assertion failures and the test results from last week’s practice, fix the bugs using IntelliJ debugging tools so that all the assertions pass.

Exercise 3: Fix an implementation of insertion sort

In the following code segment, the insertion sort algorithm is implemented with 3 methods: insertionSort() iterates through an array of integers and calls insert() on each one of them; insert() focuses on a certain integer in the array, looks at the pre-sorted subarray preceding it, and inserts it into the right spot; move() takes a subarray delimited by the pointers begin and end and moves it rightward by one place, to make room for the insertion. Move the file Sort.java in starting_files into the src folder of your IntelliJ project. Test and debug the sorting program using IntelliJ debugging tools.

static void insertionSort(int[] nums) {
    for (int i = 1; i < nums.length; i++) {
        insert(nums, i);
    }
}
static void insert(int[] nums, int i) {
    for (int j = 0; j < i; j++) {
        if (nums[j] > nums[i]) {
            int n = nums[i];
            move(nums, j, i);
            nums[j] = n;
        }
    }
}
static void move(int[] nums, int begin, int end) {
    for (int i = begin; i < end; i++) {
        nums[i + 1] = nums[i];
    }
}

[!TIP] 🔗 Solution Code