Question

Problem 1

• Create a new project called Lab7
• Create a class in that project called ListORama
• Write a static method in that class called makeLists that takes no parameters and returns no value
• In makeLists, create an ArrayList object called avengers that can hold String objects.

Problem 2

• Add the following names to the avengers list, one at a time:

Chris, Robert, Scarlett, Clark, Jeremy, Gwyneth, Mark

• Print the avengers object. You will notice that the contents are displayed in between two brackets [] and separated by a comma. This is how the toString() method of the ArrayList class is implemented!
• Then use a for-each loop to print each person in the list, one per line.

Problem 3

• Print a blank line.
• Print the current size of the ArrayList:

Current size of avengers: xxx

• Now use a regular for loop to print the elements of the list, one per line.

Problem 4

• Now remove the "Clark" and "Gwyneth" elements from the ArrayList. Remember, the list "closes the gaps" when something is removed.
• Print the current size again.

Now the size is: xxx

• Print the entire list object again.
• Make sure you removed the right people!

Problem 5

• Add "Chris H." to the end of the ArrayList.
• Change the first element "Chris" to "Chris E."
• Insert "Loki" between "Robert" and "Scarlett"
• Print the size of the ArrayList again.
• Print the entire list again.

Problem 6

• Print the elements of the ArrayList again, this time on one line separated by commas.
• Don't print a comma after the last name!
• To do this, use a regular for loop and the ArrayList get method to get each name to print.
• Use an if statement to decide whether to print a comma after each name

Answer 1

Java code:

import java.util.ArrayList;

public class ListORama {
    public static void makeLists() {
        // Problem 1
        ArrayList<String> avengers = new ArrayList<String>();

        // Problem 2
        avengers.add("Chris");
        avengers.add("Robert");
        avengers.add("Scarlett");
        avengers.add("Clark");
        avengers.add("Jeremy");
        avengers.add("Gwyneth");
        avengers.add("Mark");
        System.out.println(avengers);
        for (String avenger : avengers)
            System.out.println(avenger);

        // Problem 3
        System.out.println();
        System.out.println("Current size of avengers: " + avengers.size());
        for (int i = 0; i < avengers.size(); i++)
            System.out.println(avengers.get(i));

        // Problem 4
        avengers.remove("Clark");
        avengers.remove("Gwyneth");
        System.out.println("Now the size is: " + avengers.size());
        System.out.println(avengers);

        // Problem 5
        avengers.add("Chris H.");
        avengers.set(0, "Chris E.");
        avengers.add(2, "Loki");
        System.out.println("Now the size is: " + avengers.size());
        System.out.println(avengers);

        // Problem 6
        for (int i = 0; i < avengers.size(); i++) {
            if (i == avengers.size() - 1)
                System.out.println(avengers.get(i));
            else
                System.out.print(avengers.get(i) + ", ");
        }
    }
}

Output:

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