Questions and Exercises: Objects


  1. What's wrong with the following program?

    public class SomethingIsWrong {
        public static void main(String[] args) {
            Rectangle myRect;
            myRect.width = 40;
            myRect.height = 50;
            System.out.println("myRect's area is " + myRect.area());
  2. The following code creates one array and one string object. How many references to those objects exist after the code executes? Is either object eligible for garbage collection?

    String[] students = new String[10];
    String studentName = "Peter Parker";
    students[0] = studentName;
    studentName = null;
  3. How does a program destroy an object that it creates?


  1. Fix the program called SomethingIsWrong shown in Question 1.

  2. Given the following class, called NumberHolder , write some code that creates an instance of the class, initializes its two member variables, and then displays the value of each member variable.

    public class NumberHolder {
        public int anInt;
        public float aFloat;

Check your answers.