CSC 210 Practice Exercises PDF

Classes, Methods, Interfaces CSC 210 Practice Exercises Concept questions 1. What is the best practice for declaring instance variables? 2. What differentiates an instance variable from a class variable? 3. Why do we make instance variables private and wr...

Classes, Methods, Interfaces CSC 210 Practice Exercises Concept questions 1. What is the best practice for declaring instance variables? 2. What differentiates an instance variable from a class variable? 3. Why do we make instance variables private and write public setter and getter methods? 4. What are the keywords to declare a class constant? 5. What’s overloading? 6. What do we call a method with the same name as the class and with no return type 7. What keyword is used when we want to make use of an interface? JUnit Given the class below, write a test class with the following JUnit assertions: Assert.assertEquals() Assert.assertNotNull() Assert.assertNull() Assert.assertTrue() public class MyClass { private String x; private int y; public boolean isLonger(int size) { return x.length() > size; } public void setX(String x) { this.x = x; 1  } public void setY(int y) { this.y = y; } public String getX() { return x; } public int getY() { return y; } } Here’s what you need for import statements and class set up: import static org.junit.jupiter.api.Assertions.*; import org.junit.jupiter.api.Test; class TestMyClass { @Test void test() { // write your assertion here } } Interfaces Implement a class for the following interface: public interface Bicycle { void changeCadence(int newValue); void changeGear(int newValue); 2  void speedUp(int increment); void applyBrakes(int decrement); } Answers Concept questions 1. declare them private and write getter and setter methods 2. class variables are declared static while instance variables do not use this keyword, so that each object attributes can be set individually 3. In Java, encapsulation is achieved by declaring instance variables as private and im- plementing public getters and setters. Encapsulation is a key aspect of object-oriented programming, as it involves concealing the implementation details from outside access and providing a public interface for interaction. By implementing getters and setters, a class can enforce its own data validation rules and maintain a consistent internal state. 4. final static 5. Using the same name for two methods or more methods, with different signatures (the parameters they take are different) 6. A constructor 7. implements JUnit import static org.junit.jupiter.api.Assertions.*; import org.junit.jupiter.api.Test; class TestMyClass { @Test void testEquals() { MyClass objectOne = new MyClass(); objectOne.setX("something"); assertEquals("something", objectOne.getX()); } 3  @Test void testNull() { MyClass objectOne = new MyClass(); assertNull(objectOne.getX()); } @Test void testNotNull() { MyClass objectOne = new MyClass(); objectOne.setX("something"); assertNotNull(objectOne.getX()); } @Test void testTrue() { MyClass objectOne = new MyClass(); objectOne.setX("something"); assertTrue(objectOne.isLonger(2)); } } Interfaces public class ACMEBicycle implements Bicycle { int cadence = 0; int speed = 0; int gear = 1; // The compiler will now require that methods // changeCadence, changeGear, speedUp, and applyBrakes // all be implemented. Compilation will fail if those // methods are missing from this class. public void changeCadence(int newValue) { cadence = newValue; } public void changeGear(int newValue) { gear = newValue; 4  } public void speedUp(int increment) { speed = speed + increment; } public void applyBrakes(int decrement) { speed = speed - decrement; } public void printStates() { System.out.println("cadence:" + cadence + " speed:" + speed + " gear:" + gear); } } 5