Intermediate Java

05 - Data Structures: Lists

Anca Todirica

Goals

  • Understand the concept of lists in programming
  • Make exercises with Java implementation of lists

Slides

Exercises

Exercise 1

Build a train using ArrayList and LinkedList. Create an ArrayList that holds the waggons, then create a LinkedList that contains the waggons and has also a locomotive. Print the train in the console.


😎 Toggle Solution 
public static void main(String[] args) {
        ArrayList<String> waggons = new ArrayList<String>(Arrays.asList("wagon1", "wagon2", "wagon3"));

        LinkedList<String> train = new LinkedList<String>(waggons);

        train.addFirst("locomotive");

        for (String node : train) {
            System.out.print(node + " ");
        }
}

Exercise 2

Write a method that returns the Fibonacci sequence. The size of the sequence to be generated should be given as a parameter.


😎 Toggle Solution 
public static ArrayList<Integer> getFibonacciSequence(int numberOfItems) {
    ArrayList<Integer> fibonacci = new ArrayList<>(Arrays.asList(1,1));

    for (int i = 2; i < numberOfItems; i++) {
        fibonacci.add(fibonacci.get(i - 1) + fibonacci.get(i - 2));
    }

    return fibonacci;
}

Exercise 3

Create a method that checks if 2 lists have the same items. If the 2 lists have the same items, print in the console The lists are identical otherwise print The lists are different.


😎 Toggle Solution 
public static boolean areListsIdentical(ArrayList<String> list1, ArrayList<String> list2) {
    if (list1.size() != list2.size()) {
        return false;
    }
    
    if (!list1.containsAll(list2)) {
        return false;
    }

    return true;
}

Exercise 4

Create a method that generates a matrix using Lists. The rows will have ascending sizes. First row will have size 1, second size 2 and so one. Give the number of rows as a parameter to the method. i.e. for a matrix of size 3, the matrix should look like this:

0
0 0
0 0 0

😎 Toggle Solution 
public static void main(String[] args) {
    ArrayList<ArrayList<Integer>> matrix = generateMatrix(5);

    //iterate trough the rows
    for (int i = 0; i < matrix.size(); i++) {
        //get row one by one at position i
        ArrayList<Integer> row = matrix.get(i);
        // iterate trough the items of the row (columns) and print
        for (int j = 0; j < row.size(); j++) {
            System.out.print(row.get(j) + " ");
        }
        System.out.println();
    }
}

public static ArrayList<ArrayList<Integer>> generateMatrix(int size) {
    ArrayList<ArrayList<Integer>> matrix = new ArrayList<>(size);
    //iterate trough the number of rows
    for (int i = 0; i < size; i++) {
        // create a new ArrayList for each row, with i number of items
        ArrayList<Integer> row = new ArrayList<>(i);
        for (int j = 0; j <= i; j++) {
            row.add(0);
        }
        matrix.add(row);
    }
    return matrix;
}

Homework

  1. Implement a Java program that interleaves 2 lists in a third list. For example, given listA = {1,2,3} and listB = {4,5,6}, listC should be listC = {1,4,2,5,3,6}

  2. Given a list, print in the console the sorted list. Then, reverse the list and print it to the console.

Example:

Given the following list

list = {5, 2, 10, 6, 8, 3}

The sorted list will be:

sotedList = {2, 3, 5, 6, 8, 10}

The reversed list will be:

reveresedList = {10, 8, 6, 5, 3, 2}

Advanced

If you did OOP before, you can try to do some exercises with an actual implementation of the list.

Additional Resources

Last Updated: 2/7/2019, 7:01:32 AM

← 06 - Data Structures: Sets →