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Using methods inherited from the base class Object
Extending Classes and More example from a Well House Consultants training course
More on Extending Classes and More [link]
Source code: Lunch.java Module: J710
public class Lunch {
/* Using methods inherited from the base class Object Every Java object inherits from the base class Object - whether it's through another intermediate class or directly. If you don't declare that a class extends anthing, it defaults to extending Object. The Object base class provides methods such as: toString - Converts an obect to a string (default result - "type@address") equal - Returns true if both pint to one and the same object clone - Returns a duplicate object (not a duplicated pointer) finalize - tidies up when the garbage collector releases memory (descructor) getClass - returns a class object to tell you the object type hashCode - returns a hash code value for the object There are also methods associated with threading - wait ... notify ... notifyAll Methods such as toString and equal are designed for you to override in your own classes, providing apporpriate string representions for your objects when you output them without calling a specific method, and a comparator which lets you identify if two objects or a particular type are the same. */ public String Descriptor; private int portions; int cals; // No "p" word so "package" ;-) protected Lunch (String Descriptor, int portions, int cals) { this.Descriptor = Descriptor; this.portions = portions; this.cals = cals; } public String toString() { String About = "Type = " + "Lunch" + "; Product = " + this.Descriptor + "; Portions = " + this.portions + ";"; return About; } public boolean equals(Lunch that) { return (this.cals == that.cals); } public static void main ( String [] args) { Lunch [] Item = new Lunch[6]; Item[0] = new Lunch("Chilli Con Carne",4,175); Item[1] = new Lunch("Roast Potatoes",5,160); Item[2] = new Lunch("Chicken Drumsticks",3,175); Item[3] = new Lunch("Fresh Fruit Salad",4,120); Item[4] = new Lunch("Roombikkies",35,120); Item[5] = new Lunch("Coffee",66,10); for (int k=0; k<Item.length; k++) { System.out.println(Item[k]); } // To test "equals" - anything like anything else? for (int j=0; j<Item.length-1; j++) { Lunch Maybe = Item[j]; for (int k=j+1; k<Item.length; k++) { if (Maybe.equals(Item[k])) { System.out.println (Maybe + " - could substitute " + Item[k]); } } } } } /* Sample output: wizard:jn10 graham$ java Lunch Type = Lunch; Product = Chilli Con Carne; Portions = 4; Type = Lunch; Product = Roast Potatoes; Portions = 5; Type = Lunch; Product = Chicken Drumsticks; Portions = 3; Type = Lunch; Product = Fresh Fruit Salad; Portions = 4; Type = Lunch; Product = Roombikkies; Portions = 35; Type = Lunch; Product = Coffee; Portions = 66; Type = Lunch; Product = Chilli Con Carne; Portions = 4; - could substitute Type = Lunch; Product = Chicken Drumsticks; Portions = 3; Type = Lunch; Product = Fresh Fruit Salad; Portions = 4; - could substitute Type = Lunch; Product = Roombikkies; Portions = 35; wizard:jn10 graham$ */ Learn about this subject
This module and example are covered on the following public courses:
* Learning to Program in Java * Java Bootcamp * Java Programming for the Web Also available on on site courses for larger groups Books covering this topic
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