Lecture 11 Objectives [Nov 10]prev next

MUSICAL COMPOSITION: Beethoven Symphony no. 7, Karajan Conductor.
 

Movements I - IV 33:30

At the end of today's class you should

HAVE READ:

• [209-218][218-233]

KNOW:

• Concept of Overloading
• Concept of Constructors, with multiple forms
• Understand this parameter in context of constructors [p. 226]
• Understand why certain code (i.e., input from the console) must not be included in the constructor.

BE ABLE TO:

• Write two methods for a class that have the same name, yet different parameter types and/or number
• Write multiple constructors that each (in essence) use the same core constructor code as the single-point of access.

DAILY QUESTION:

• You are given the CelsiusTemperature class from Nov-09 (shown below). There are two fragments of code below that start by instantiating an instance of the CelsiusTemperature class to represent the temperature 23.2 degrees celsius. At the end of both fragments, variable ct refers to a CelsiusTemperature object whose value represents 10.2 degrees celsius. Explain the difference between the two code fragments, and explain why fragment two is preferred:
  
   

  Fragment One	Fragment Two
  CelsiusTemperature ct = new CelsiusTemperature (23.2); ct = new CelsiusTemperature (10.2);	CelsiusTemperature ct = new CelsiusTemperature (23.2); ct.setTemperature (10.2);

   

  public class CelsiusTemperature {   /** Temperature. */   private double value;   /** Constructor for CelsiusTemperature, takes in desired value to initialize object. */   public CelsiusTemperature (double temp) {     setTemperature (temp);   }   /**   * Set temperature to the desired value.   *   * Ensure that newVal >= -273.15 (absolute zero on celsius scale).   *   * @param newVal the desired new value.   */   public void setTemperature (double newVal) {     if (newVal < -273.15) {       System.err.println ("Attempt to set value less than allowed.");       return;     }     value = newVal;   } }

   

Sample Exam Question:

1. You are asked to write a TemperatureRecorder, which is capable of recording temperatures that are either CelsiusTemperatire, FahrenheitTemperature, or KelvinTemperature. Describe the signatures of the methods you would add to the TemperatureRecorder class. Note: don't write the implementation! Just describe the signatures.