Review Questions

Which statements are true about collections?

Select the two correct answers.

What will be the result of attempting to compile and run the following program?

import java.util.*;

public class Sets {
    public static void main(String[] args) {
        HashSet set1 = new HashSet();
        addRange(set1, 1);
        ArrayList list1 = new ArrayList();
        addRange(list1, 2);
        TreeSet set2 = new TreeSet();
        addRange(set2, 3);
        LinkedList list2 = new LinkedList();
        addRange(list2, 5);

        set1.removeAll(list1);
        list1.addAll(set2);
        list2.addAll(list1);
        set1.removeAll(list2);

        System.out.println(set1);
    }
    static void addRange(Collection col, int step) {
        for (int i = step*2; i<=25; i+=step)
            col.add(new Integer(i));
    }
}

Select the one correct answer.

Which of these methods are defined in the Collection interface?

Select the three correct answers.

What will be the output from the following program?

import java.util.*;
public class Iterate {
    public static void main(String[] args) {
        List l = new ArrayList();
        l.add("A"); l.add("B"); l.add("C"); l.add("D"); l.add("E");
        ListIterator i = l.listIterator();
        i.next(); i.next(); i.next(); i.next();
        i.remove();
        i.previous(); i.previous();
        i.remove();
        System.out.println(l);
    };
};

Select the one correct answer.

Which of these methods from the Collection interface will return the value true if the collection was modified during the operation?

Select the two correct answers.