Create 12A Object's inside calls

Week 4: Writing classes/12A Object's inside calls

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+
+The METHODS of an object can also CALL OTHER METHODS of the SAME OBJECT. 
+This is important to ensure modularity: 
+this way the same code does not need to be written several times inside the same class, but the same methods can be used.
+
+A method within the same class is called by its name WITHOUT a PREFIX 
+(although you CAN PREFIX the call with the keyword 'this' if you wish, IF it makes the code CLEARER).
+
+An example where the constructor of the 'Car' class calls the setting method 
+to check if the registration number is in the allowed format 
+(the actual check is quite loose in the implementation, though) - this way, 
+the check does NOt NEED to be IMPLEMENTed SEPARATELY for the constructor and the setting method:
+
+class Car {
+    // CLASS ATTRIBUTES
+    private String brand;
+    private String licensePlate;
+
+    // CONSTRUCTOR
+    public Car(String brand, String licensePlate) {
+        this.brand = brand;
+        // Also
+        // this.setLicensePlate(licensePlate); 
+        // would be ok
+        setLicensePlate(licensePlate);
+    }
+
+    public String getBrand() {
+        return brand;
+    }
+
+    public void setBrand(String brand) {
+        this.brand = brand;
+    }
+
+    public String getLicensePlate() {
+        return licensePlate;
+    }
+
+    public void setLicensePlate(String licensePlate) {
+        if (licensePlate.length() >= 3 && licensePlate.contains("-")) {
+            this.licensePlate = licensePlate;
+        } 
+    }  
+}
+
+
+
+// then save as TestClass.java
+// move 'TestClass' code segment above 'Car' code segment
+Testclass:
+public class TestClass {
+    public static void main(String[] args) {
+        // this is ok
+        Car car = new Car("Lada", "abc-123");
+        System.out.println(car.getLicensePlate());
+        
+        // this is NOT 'SET'
+        // because it fails the format check
+        car.setLicensePlate("x123");
+        System.out.println(car.getLicensePlate());
+        
+        // this is NOT CREATED
+        // because it fails the format check
+        Car car2 = new Car("Mersu", "x-");
+        System.out.println(car2.getLicensePlate());    
+    }
+}
+
+Program outputs:
+abc-123
+abc-123
+null
+
+
+
+