1- Differentiate between extends and implements keywords in java? 2- What is wrong with this code:

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1 1- Differentiate between extends and implements keywords in java? 2- What is wrong with this code: public double getsalary() double basesalary = getsalary(); return basesalary + bonus; 3- What does the word super mean in java? 4- super does the same as this keyword? (true/false) 5- What is wrong with this code: public Manager(String n, double s, int year, int month, int day) bonus = 0; super(n, s, year, month, day); 6- What will happen in the following scenarios in terms of calling the superclass constructors. A. A subclass constructor does not call a superclass constructor explicitly B. A subclass constructor does not call a superclass constructor explicitly and the superclass does not implement the default constructor 7- Do I need to declare methods in java as virtual? 8- In the Java programming language, object variables are polymorphic (true/false)? 9- What might go wrong with the following assignment : (Manager is a subclass of Employee) Manager[] managers = new Manager[10]; Employee[] staff = managers; 10- Having a derived class form a superclass,we can override a method using different return type. (True/false) 11- What actually happens when you use dynamic binding to call a method? 12- when you override a method, it does not matter to change the visibility of the method (true/false)? E.g. you change the method from public to private. 13- What does it mean to have a final class or final method? 14- When a class is defined as final, all of its members and fields are treated as final (true/false)? 15- How, in C++, can you prevent a base class from being inherited? 16- What is the difference between the following two pieces of code and which one is better? Is it acceptable in all cases to do so? A:

2 Manager boss = (Manager) staff[1]; B: if (staff[1] instanceof Manager) boss = (Manager) staff[1]; Does null considered as an object in java? 18- Differentiate among the following modifiers private, public, protected, and without modifier? 19- What is the cosmic root class in java? 20- What are the properties of equals method in java? 21- What is the difference between the following two statements: A. if (!(otherobject instanceof Employee)) return false; B. if (!(otherobject.equals (Employee))) return false; 22- Does the following equals method overrides the one in the object class: public class Employee public boolean equals(employee other) return name.equals(other.name) && salary == other.salary && hireday.equals(other.hireday);...

3 23- What is the output of the following code: String s = "Ok"; StringBuilder sb = new StringBuilder(s); String t = new String("Ok"); StringBuilder tb = new StringBuilder(t); If (s.hashcode() == t.hashcode()) System.out.println(" The two string hashes are equal "); System.out.println(" The two string hashes are not equal "); If (tb.hashcode() == sb.hashcode()) System.out.println(" The two stringbuilders hashes are equal "); System.out.println(" The two stringbuilders hashes are not equal "); 24- The hashcode () output can not be a negative value (true/false)? 25- What is the possible output of the following code: Point p = new Point(10, 20); String message = "The current position is " + p; 26- What is the possible output of the following code : System.out.println(System.out) 27- What is the difference between the following two statements: new ArrayList<Employee>(100); new Employee[100]; 28- What is actually happening at the run time when executing the following code and what is the name of this process: ArrayList<Integer> list = new ArrayList<Integer>(); list.add(3); list.add(3); 29- What is the output of the following code? And why? What is the solution? Integer a = 1000; Integer b = 1000; if (a == b) System.out.println("equal "); System.out.println(" Not equal ");

4 30- What is wrong with the following method: public static void triple(integer x) x = 3 * x; 31- What it takes to do the following in java: A- Ask for a class name. B- Create an object of that class. C- Show the field names for the object and their values. 32- What is the functionality of instanceof()? Explain what actually happen when executing this code in C++: public class BaseType public BaseType() Console.WriteLine("Call base ctor."); DoSomething(); public virtual void DoSomething() Console.WriteLine("Base DoSomething"); public class DerivedType : BaseType public DerivedType() Console.WriteLine("Call derived ctor."); public override void DoSomething() Console.WriteLine("Derived DoSomething"); public class MainClass public static void Main() DerivedType derived = new DerivedType(); Console.ReadLine();

5 34- Explain what exactly happen when executing the following statement : x=y=z=15;