Learning Help

[Carlos]

Hi Everybody,

Im doing a course that involves learning java, and im findind it abit tough. I have a piece of work to do, which involves writing a class that tests another class to see if its methods work, and i have no idea where to start. I heard from a pal this is a great place to get advice, so thought id see if anybody could help. Thanks in Advance.

Carl

[sjalle]

This is the Car class and a class to test its methods.

/**
 * Class for testing the Car class.
 * This class doesn't need a constructor, but I've supplied
 * a default (empty) constructor here
 */
class CarClassTester {
  public CarClassTester() {} // empty constructor

  public void runTest() {
    // make some cars
    Car aCar=new Car("Ford","Focus",2003);
    Car anotherCar=new Car("Volvo","V70",2004);
    // get the make, model and year of one of the cars
    // and print it out.
    String mk=aCar.getMake();
    String md=aCar.getModel();
    int yr=aCar.getYear();
    System.out.println("Car data, Make: "+mk+", Model: "+md+", Year: "+yr);
    // use the toString method of both car objects.  
    System.out.println(anotherCar.toString());
    System.out.println(aCar.toString());
  }
  // the main method, this is where the program execution starts.
  // the definition of this method requires the String array parameter
  // but that array is not used here.
  public static void main(String[] args) {
    // create a CarClassTester object
    CarClassTester cct = new CarClassTester();
    // invoke the CarClassTester objetcs only method.
    cct.runTest();
    // and we are finished ....
  }
}

/**
 * Class for storing basic car information
 */
class Car {
  private String make = null;
  private String model = null;
  private int year = -1;

  // constructor
  public Car(String make, String model, int year) {
    this.make = make;
    this.model = model;
    this.year = year;
  }

  // the toString method, delivers a string explainig in
  // short what the object contains
  public String toString() {
    return "Make: " + make + ", Model: " + model + ", Year: " + year;
  }

  // get methods
  public String getMake() {
    return make;
  }

  public String getModel() {
    return model;
  }

  public int getYear() {
    return year;
  }
}

[Carlos]

Thanks that really helped me to understand what i have to do, however im getting a few porblems you could perhaps help iron out, heres my Class, and my Class tester;

/**
 * Details of Technical support calls.
 * The details of the calls are a reference number, the call's priority,
 * the email address of the caller and a description of the call.
 * 
 */

public class Call
{

  private int number;
  private int priority;
  private String caller;
  private String description;

  /**
  * Class Constructor. 
  * Setting default values.
  */
  public Call ()
  {
    number = 0;
    priority = 0;
    caller = "";
    description = "";
  }

  /**
   * Class Constructor. 
   * Set initial values to those provided as parameters.
   *
   * @param number Initial number.
   * @param priority Initial priority.
   * @param caller Initial caller name.
   * @param description Initial call description.
   */
  public Call (int number, int priority, String caller, String description)
  {
    this.number = number;
    this.priority = priority;
    this.caller = caller;
    this.description = description;
  }

  /**
   * Accessor for Call Reference Number.
   *
   * @return Call reference number.
   */
  public int getNumber ()
  {
    return number;
  }

  /**
   * Accessor for Call Priority.
   *
   * @return Call priority.
   */
  public int getPriority ()
  {
    return priority;
  }

  /**
   * Accessor for Call Caller.
   *
   * @return Call's caller (email address).
   */
  public String getCaller ()
  {
    return caller;
  }

  /**
   * Accessor for Call Description.
   *
   * @return Call description.
   */
  public String getDescription ()
  {
    return description;
  }

  /**
   * Mutator for Call Reference Number.
   *
   * @param number New call reference number.
   * @return true if call reference number is set, false otherwise.
   */
  public boolean setNumber (int number)
  {
    if (number > 0) {
      this.number = number;
      return true;
    }

    return false;
  }

  /**
   * Mutator for Call Priority.
   * Call priority must be 1, 2, 3, or 4. The mutator enforces this, and
   * returns a value to show whether an invalid value is provided.
   *
   * @param priority New call priority.
   * @return true if call priority is set, false otherwise.
   */
  public boolean setPriority (int priority)
  {
    if (priority >= 1 && priority <= 4) {
      this.priority = priority;
      return true;
    }
    else {
      return false;
    }
  }

  /**
   * Mutator for Call Caller.
   * The caller must (appear to) be a valid email address. The mutator
   * attempts to enforce this by checking that it contains an @ symbol
   * and at least one dot.
   *
   * @param caller New call caller.
   * @return true if caller is set, false otherwise.
   */
  public boolean setCaller (String caller)
  {
    if (caller.indexOf ('.') == -1 || caller.indexOf ('@') == -1) {
      return false;
    }
    else {
      this.caller = caller;
      return true;
    }
  }

  /**
   * Mutator for Call Description.
   * The description is any non-zero sequence of characters.
   *
   * @param description New call description.
   * @return true if description is set, false otherwise.
   */
  public boolean setDescription (String description)
  {
    if (description.length () > 0) {
      this.description = description;
      return true;
    }
    else {
      return false;
    }
  }

  /**
   * String Representation.
   * The call details are formatted in a small table:<br>
   * <pre>
   * Call#: 0 (Priority: 0) (Caller: john@doe.com)
   * Description:
   *   Example call.
   * </pre>
   * @return String representation.
   */
  public String toString ()
  {
    String c = "";

    c += "Call# " + number + " (Priority: " + priority + ") ";
    c += "(Caller: " + caller + ")\n";

    c+= "Description:\n" + description + '\n';

    return c;
  }
}

Thats the class i need to write a tester for, and heres what i came up with thanks to your help;

/**
 * Class for testing the Call Methods
 */
class CallTest {
  public CallTest() {} // constructor

  public void runTest() {
    // Add some calls
    Call aCall=new Call("1","4","test@test.com","Broken Monitor");
    Call anotherCall=new Call("2","1","test2@test2.com","Computer on Fire");
    // get the number, priority, email address and Description of the call
    // and print it out.
    int num=aCall.getNumber();
    int pri=aCall.getPriority();
    String caller=aCall.getCaller();
    String descrip=aCall.getDescription();
    System.out.println("Call Data, Reference Number: "+num+", Priority: "+pri+", Caller Id: "+caller+", Description: "+descrip);
    // use the toString method of both call objects.  
    System.out.println(anotherCall.toString());
    System.out.println(aCall.toString());
  }
  // the main method, runs the program and tests it.
  public static void main(String[] args) {
    // create a CallTest object
    CallTest cct = new CallTest();
    // invoke the CallTest objetcs only method.
    cct.runTest();
    // tests are run
  }
}

However, when i try to compile it, i get the error "cannot find symbol constructor.Call" on lines 9 and 10. Any ideas? Thanks again for such excellent help

Carl

EDIt : Realised i was quoting the intergers! Thanks for the help!!!

[prometheuzz]

Dear Carl,

You are trying to contsruct a Call-object with four String's:

Call aCall=new Call("1","4","test@test.com","Broken Monitor");
Call anotherCall=new Call("2","1","test2@test2.com","Computer on Fire");

However, the right way to create a Call-object is two int's followed by two String's. An int is a natural number and a String is a list of characters.

This is how to tell java:

int i = 1;
double d = 1.0;
char c = 'a';
String s = "testing 1 2 ...";

So, the correct way to construct a Call-objetc is like this:

Call aCall=new Call(1,4,"test@test.com","Broken Monitor");
Call anotherCall=new Call(2,1,"test2@test2.com","Computer on Fire");

Good luck with your class!