by Ken Arnold, James Gosling and David Holmes (2005)

Table of Contents

Source Code

tjpl4e

Classes and Objects

In Java, programmers must explicitly create an object. For example, in C++, Body mercury; will create an object with default values, but in Java, it is just a declaration; mercury is a reference to an object of type Body.

Exercises

Exercise 2.1: Write a simple Vehicle class that has fields for (at least) current speed, current direction in degrees, and owner name.

class Vehicle {
    public float speed;
    public int degree;
    public String owner;
}

Exercise 2.2: Write a LinkedList class that has a field of type Object and a reference to the next LinkedList element in the list.

class LinkedList {
    public Object obj;
    public LinkedList next;
}

Exercise 2.3: Add a static field to your Vehicle class to hold the next vehicle identification number, and a non-static field to the Vehicle class to hold each car’s ID number.

class Vehicle {
    public long ID;
    public float speed;
    public int degree;
    public String owner;

    public static long nextID = 0;
}