Changes between Version 15 and Version 16 of ControlSystems/SoftwareTeam/Training/GettingStarted/IntroJava

Timestamp:

Oct 12, 2019, 11:03:34 PM (6 years ago)

Author:

David Albert

Comment:

--

ControlSystems/SoftwareTeam/Training/GettingStarted/IntroJava

@@ -199 +199 @@
 When a class extends another class, it inherits all of the attributes and functions of the parent (super) class.  
 
-Create a new folder (InheritanceExample) and in it create the following java files:
+Create a new folder (!InheritanceExample) and in it create the following java files:
 
 Fruit.java:
@@ -282 +282 @@
   * the use of the super.eat() call to invoke the eat method of the extended super class (Fruit)
 
+
+==== Class containment
+Sometimes it's useful to model the containment relationship between classes.  For example, consider the following classes:
+
+Plane.java:
+{{{
+import java.util.ArrayList;
+
+public class Plane {
+    ArrayList<Passenger> passengers;
+    int seats;
+
+    public Plane(int seats) {
+        this.seats = seats;
+        passengers = new ArrayList<>();
+    }
+
+    public void board(Passenger p) {
+        if (passengers.size() < seats) {
+            passengers.add(p);
+        } else {
+            System.out.println("Sorry, plane is full.");
+        }
+    }
+
+    public int weight() {
+        int w=0;
+        for (Passenger p:passengers) {
+             w += p.weight;
+        }
+        return w;
+    }
+}
+}}}
+
+Passenger.java
+{{{
+public class Passenger {
+    public int weight;
+    String name;
+
+    public Passenger(String name, int weight) {
+        this.name = name;
+        this.weight=weight;
+    }
+}
+}}}
+
+Containment.java
+{{{
+public class Containment {
+    public static void main(String args[]) {
+        Plane puddleHopper = new Plane(10);
+        Passenger p1 = new Passenger("Bob", 180);
+        Passenger p2 = new Passenger("Alice", 135);
+
+        puddleHopper.board(p1);
+        puddleHopper.board(p2);
+
+        System.out.println("Passengers weigh "+puddleHopper.weight()+" lbs");
+    }
+}
+}}}
+
 == Princeton Java
 There's a lot to programming and you'll get to the fun stuff a lot faster if you do some self-study.  There are many Java tutorials, but if you'd like to try learning the Princeton way, try [https://introcs.cs.princeton.edu/java/home/ this one].