public static dtype STATICVARIABLEINCAPS = <value>;

Week 6: Methods of OO Programming/03A. Class variables = STATIC VARIABLES

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+It is also possible to define 'static variables'. 
+These are also called 'class variables'. 
+Hence, they are used by using the class name, not an object reference.
+
+Class variables are OFTEN 'public'. 
+The name is typically written in ALL CAPS.
+
+class FootballMatch {
+    // Class variables are defined before attributes
+    public static int TIME_IN_MINUTES = 90;
+    
+    private String team1;
+    private String team2;
+    
+    public FootballMatch(String team1, String team2) {
+        this.team1 = team1;
+        this.team2 = team2;
+    }
+    
+    // etc.
+}
+
+
+
+Example of using the variable:
+public class Test {
+    public static void main(String[] args) {
+        // Variable can be references withou creating an object
+        int duration = FootballMatch.TIME_IN_MINUTES;
+        System.out.println("Football match takes " + duration + " minutes.");
+    }
+}
+Program outputs:
+Football match takes 90 minutes.
+
+
+
+
+
+
+
+
+
+
+Earlier in Java, it was typical to use class variables to define different kinds of class constants - for example the suits of the cards. 
+Later, 'enum classes' were introduced for this (these are discussed next week).
+
+Let's see another example of class variables. 
+Now, the value of the class variable is changed each time an object is created.
+
+Note that since it is a class variable, there is only 1 SHARED VALUE for ALL OBJECTS CREATED from the class.
+..BUT U CAN CHANGE FROM THE 'DEFAULT SHARED VALUE' TO AN OBJECT-SPECIFC VALUE/SMTH ELSE!!!!!!!!!!!
+
+ 
+
+class Bubble {
+    public static int BUBBLES_NOW = 0;
+    
+    private int diameter;
+    
+    public Bubble(int diameter) {
+        this.diameter = diameter;
+        Bubble.BUBBLES_NOW++;
+    }
+}
+ 
+
+Example about using the variable:
+public class TestClass {
+    public static void main(String[] args) {
+        Bubble bubble1 = new Bubble(5);
+        System.out.println(Bubble.BUBBLES_NOW);
+        
+        Bubble bubble2 = new Bubble(21);
+        System.out.println(Bubble.BUBBLES_NOW);
+        
+        Bubble bubble3 = new Bubble(15);
+        System.out.println(Bubble.BUBBLES_NOW);
+        
+        Bubble bubble4 = new Bubble(7);
+        System.out.println(Bubble.BUBBLES_NOW);
+    }
+}
+
+Program outputs:
+1
+2
+3
+4
+
+
+