Inheritance with Java GUI

Prepare a input form which will take 2 input for range of values. After getting input from the user, find sum of all primes from the given range using a button named Generate-Sum. After getting the sum check whether the sum is even or not.  All the process will be done by a class followed by Inheritance in Java. You have to display the output in a label at Form.

Inheritance in Java Programming

Inheritance in java is a mechanism in which one object acquires all the properties and behaviors of parent object.
The idea behind inheritance in java is that you can create new classes that are built upon existing classes. When you inherit from an existing class, you can reuse methods and fields of parent class, and you can add new methods and fields also.
Inheritance represents the IS-A relationship, also known as parent-child relationship.

Why use inheritance in java

• For Method Overriding (so runtime polymorphism can be achieved).
• For Code Reusability.

Syntax of Java Inheritance

1. class Subclass-name extends Superclass-name  
2. {  
3.    //methods and fields  
4. }  

The extends keyword indicates that you are making a new class that derives from an existing class.
In the terminology of Java, a class that is inherited is called a super class. The new class is called a subclass.

---

Understanding the simple example of inheritance

 

 As displayed in the above figure, Programmer is the subclass and Employee is the superclass. Relationship between two classes is Programmer IS-A Employee.It means that Programmer is a type of Employee.

1. class Employee{  
2.  float salary=40000;  
3. }  
4. class Programmer extends Employee{  
5.  int bonus=10000;  
6.  public static void main(String args[]){  
7.    Programmer p=new Programmer();  
8.    System.out.println("Programmer salary is:"+p.salary);  
9.    System.out.println("Bonus of Programmer is:"+p.bonus);  
10. }  
11. }  

 Programmer salary is:40000.0
 Bonus of programmer is:10000

In the above example, Programmer object can access the field of own class as well as of Employee class i.e. code reusability.

---

Types of inheritance in java

On the basis of class, there can be three types of inheritance in java: single, multilevel and hierarchical.
In java programming, multiple and hybrid inheritance is supported through interface only. We will learn about interfaces later.

 

Note: Multiple inheritance is not supported in java through class.

When a class extends multiple classes i.e. known as multiple inheritance. For Example:

---

Why multiple inheritance is not supported in java?

To reduce the complexity and simplify the language, multiple inheritance is not supported in java.
Consider a scenario where A, B and C are three classes. The C class inherits A and B classes. If A and B classes have same method and you call it from child class object, there will be ambiguity to call method of A or B class.
Since compile time errors are better than runtime errors, java renders compile time error if you inherit 2 classes. So whether you have same method or different, there will be compile time error now.

1. class A{  
2. void msg(){System.out.println("Hello");}  
3. }  
4. class B{  
5. void msg(){System.out.println("Welcome");}  
6. }  
7. class C extends A,B{//suppose if it were  
8.  Public Static void main(String args[]){  
9.    C obj=new C();  
10.    obj.msg();//Now which msg() method would be invoked?  
11. }  
12. }  

Compile Time Error

OOP in JAVA Quiz Questions

OBJECT ORIENTED PROGRAMMING WITH JAVA

Question: Can a private method of a super-class be declared within a subclass?

Question: Why Java does not support multiple inheritance ?

Question:What is the difference between final, finally and finalize?

Question: Where and how can you use a private constructor?

Question: In System.out.println(),what is System,out and println,pls explain?

Question: What is meant by "Abstract Interface"?

Question: Can you make an instance of an abstract class? For example - java.util.Calender is an abstract class with a method getInstance() which returns an instance of the Calender class.

Question: What is the output of x<y? a:b = p*q when x=1,y=2,p=3,q=4?

Question: What is the difference between Swing and AWT components?

Question: Why Java does not support pointers?

Question: What is a platform?

Question: What is the main difference between Java platform and other platforms?

Question: What is the Java Virtual Machine?

Question: What is the Java API?

Question: What is the package?

Question: What is native code?

Question:  Is Java code slower than native code?

Question: What is the serialization?

Question: How to make a class or a bean serializable?

Question:  Which containers use a border layout as their default layout?

Question:  What is synchronization and why is it important?

Question: What are synchronized methods and synchronized statements?

Question:  What is synchronization and why is it important?

Question: What are synchronized methods and synchronized statements?

Question: What are three ways in which a thread can enter the waiting state?

Question: Can a lock be acquired on a class?

Question: What's new with the stop(), suspend() and resume() methods in JDK 1.2?

Question: What is the preferred size of a component?

Question: What method is used to specify a container's layout?

Question: Which containers use a Flow-layout as their default layout?

Question: What is thread?

Question: What is multi threading?

Question: How does multi threading take place on a computer with a single CPU?

Question: How to create multithread in a program?

Question: Can Java object be locked down for exclusive use by a given thread?

Question: Can each Java object keep track of all the threads that want to exclusively access to it?

Question: What state does a thread enter when it terminates its processing?

Question: What invokes a thread's run() method?

Question: What is the purpose of the wait(), notify(), and notifyAll() methods?

Question: What are the high-level thread states?

Question: What is the Collections API?

Question: What is the List interface?

Question:  How does Java handle integer overflows and under-flows?

Question:  What is the Vector class?

Question: If a method is declared as protected, where may the method be accessed?

Question:  What is an Iterator interface?

Question: How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8 characters?

Question:  What is the difference between yielding and sleeping?

Question:  Is sizeof a keyword?

Question: What are wrapped classes?

Question: Does garbage collection guarantee that a program will not run out of memory?

Question: What is the difference between preemptive scheduling and time slicing?

Question: Name Component subclasses that support painting.

Question: What is a native method?

Question: How can you write a loop indefinitely?

Question:  Can an anonymous class be declared as implementing an interface and extending a class?

Question: What is the purpose of finalization?

Question: Which class is the super-class for every class.

Question: What is the difference between the Boolean & operator and the && operator?

Question: What is the GregorianCalendar class?

Question: What is the SimpleTimeZone class?

Question: Which Container method is used to cause a container to be laid out and redisplayed?

Question: What is the Properties class?

Question: What is the purpose of the Runtime class?

Question:  What is the purpose of the System class?

Question: What is the purpose of the finally clause of a try- catch-finally statement?

Question: What is the Locale class?

Question: What must a class do to implement an interface?

Question: What is an abstract method?

Question: What is a static method?

Question: What is a protected method?

Question: What is the difference between a static and a non -static inner class?

Question:  What is an object's lock and which object's have locks?

Question: When can an object reference be cast to an interface reference?

Question:  What is the difference between a Window and a Frame?

Question: What do heavy weight components mean?

Question: Which package has light weight components?

Question: What are peerless components?

Question: What is the difference between the Font and FontMetrics classes?

Question: What happens when a thread cannot acquire a lock on an object?

Question: What is the difference between the Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy?

Question: What classes of exceptions may be caught by a catch clause?

Question:What is the difference between throw and throws keywords?

Question: If a class is declared without any access modifiers, where may the class be accessed?

Question: What is the Map interface?

Question: Does a class inherit the constructors of its superclass?

Question: Name primitive Java types.

Question: Which class should you use to obtain design information about an object?

Question: How can a GUI component handle its own events?

Question: How are the elements of a GridBagLayout organized?

Question: What advantage do Java's layout managers provide over traditional windowing systems?

Question: What are the problems faced by Java programmers who don't use layout managers?

Question: What is the difference between static and non -static variables?

Question: What is the difference between the paint() and repaint() methods?

Question:  What is the purpose of the File class?

Question:  What restrictions are placed on method overloading?

Question:  What restrictions are placed on method overriding?

Question: What is casting?

Question: Name Container classes.

Question: What class allows you to read objects directly from a stream?

Question:  How are this() and super() used with constructors?

Question: How is it possible for two String objects with identical values not to be equal under the == operator?

Question: What an I/O filter?

Question: What is the Set interface?

Question:  What is the List interface?

Question: What is the purpose of the enableEvents() method?

Question: What is the difference between the File and RandomAccessFile classes?

Question: What interface must an object implement before it can be written to a stream as an object?

Question: What is the ResourceBundle class?

Question: What is the difference between a Scrollbar and a ScrollPane? Answer: A Scrollbar is a Component, but not a Container. A ScrollPane is a Container. A ScrollPane handles its own events and performs its own scrolling.

Question: What is a Java package and how is it used?

Question: What are the Object and Class classes used for?

Question: What is Serialization and deserialization?

Question: what is tunnelling?

Question: Does the code in finally block get executed if there is an exception and a return statement in a catch block?

Question: How you restrict a user to cut and paste from the html page?

Question:  Is Java a super set of JavaScript?

Question: What is a Container in a GUI?

Question: How the object oriented approach helps us keep complexity of software development under control?

Question: What is polymorphism?

Question: What is design by contract?

Question: What are use cases?

Question: What is the difference between interface and abstract class?

Question: What is an Iterator interface?

Question: What is the difference between the >> and >>> operators?

Question: Which method of the Component class is used to set the position and size of a component?

Question: How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8 characters?

Question: What is the difference between yielding and sleeping?

Question: Which java.util classes and interfaces support event handling?

Question: Is sizeof a keyword?

Question: What are wrapped classes?

Question: Does garbage collection guarantee that a program will not run out of memory?

Question: What restrictions are placed on the location of a package statement within a source code file?

Question: Can an object's finalize() method be invoked while it is reachable?

Question: What is the immediate superclass of the Applet class?

Question: What is the difference between preemptive scheduling and time slicing?

Question: Name three Component subclasses that support painting.

Question: What value does readLine() return when it has reached the end of a file?

Question: What is the immediate superclass of the Dialog class?

Question: What is clipping?

Question: What is a native method?

Question: Can a for statement loop indefinitely?

Question: What are order of precedence and associativity, and how are they used?

Question: When a thread blocks on I/O, what state does it enter?

Question: To what value is a variable of the String type automatically initialized?

Question: What is the catch or declare rule for method declarations?

Question: What is the difference between a MenuItem and a CheckboxMenuItem?

Question: What is a task's priority and how is it used in scheduling?

Question: What class is the top of the AWT event hierarchy?

Question: When a thread is created and started, what is its initial state?

Question: Can an anonymous class be declared as implementing an interface and extending a class?

Question: What is the range of the short type?

Question: What is the range of the char type?

Question: In which package are most of the AWT events that support the event-delegation model defined?

Question: What is the immediate superclass of Menu?

Question: What is the purpose of finalization?

Question: Which class is the immediate superclass of the MenuComponent class.

Question: What invokes a thread's run() method?

Question: What is the difference between the Boolean & operator and the && operator?

Question: Name three subclasses of the Component class.

Question: What is the GregorianCalendar class?

Question: Which Container method is used to cause a container to be laid out and redisplayed?

Question: What is the purpose of the Runtime class?

Question: How many times may an object's finalize() method be invoked by the garbage collector?

Question: What is the purpose of the finally clause of a try-catch-finally statement?

Question: What is the argument type of a program's main() method?

Question: Which Java operator is right associative?

Question: What is the Locale class?

Question: Can a double value be cast to a byte?

Question: What is the difference between a break statement and a continue statement?

Question: What must a class do to implement an interface?

Question: What method is invoked to cause an object to begin executing as a separate thread?

Question: Name two subclasses of the TextComponent class.

Question: What is the advantage of the event-delegation model over the earlier event-inheritance model?

Question: Which containers may have a MenuBar?

Question: How are commas used in the intialization and iterationparts of a for statement?

Question: What is the purpose of the wait(), notify(), and notifyAll() methods?

Question: What is an abstract method?

Question: How are Java source code files named?

Question: What is the relationship between the Canvas class and the Graphics class?

Question: What are the high-level thread states?

Question: What value does read() return when it has reached the end of a file?

Question: Can a Byte object be cast to a double value?

Question: What is the difference between a static and a non-static inner class?

Question: What is the difference between the String and StringBuffer classes

Question: If a variable is declared as private, where may the variable be accessed?

Question: What is an object's lock and which object's have locks?

Question: What is the Dictionary class?

Question: How are the elements of a BorderLayout organized?

Question: What is the % operator?

Question: When can an object reference be cast to an interface reference?

Question: What is the difference between a Window and a Frame?

Question: Which class is extended by all other classes?

Question: Can an object be garbage collected while it is still reachable?

Question: Is the ternary operator written x : y ? z or x ? y : z ?

Question: What is the difference between the Font and FontMetrics classes?

Question: How is rounding performed under integer division?

Question: What happens when a thread cannot acquire a lock on an object?

Question: What is the difference between the Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy?

Question: What classes of exceptions may be caught by a catch clause?

Question: If a class is declared without any access modifiers, where may the class be accessed?

Question: What is the SimpleTimeZone class?

Question: What is the Map interface?

Question: Does a class inherit the constructors of its superclass?

Question: For which statements does it make sense to use a label?

Question: What is the purpose of the System class?

Question: Which TextComponent method is used to set a TextComponent to the read-only state?

Question: How are the elements of a CardLayout organized?

Question: Is &&= a valid Java operator

Question: Name the eight primitive Java types.

Question: Which class should you use to obtain design information about an object?

Question: What is the relationship between clipping and repainting?

Question: Is "abc" a primitive value?

Question: What is the relationship between an event-listener interface and an event-adapter class?

Question: What restrictions are placed on the values of each case of a switch statement?

Question: What modifiers may be used with an interface declaration?

Question: Is a class a subclass of itself?

Question: What is the highest-level event class of the event-delegation model?

Question: What event results from the clicking of a button?

Question: How can a GUI component handle its own events?

Question: What is the difference between a while statement and a dostatement?

Question: How are the elements of a GridBagLayout organized?

Question: What advantage do Java's layout managers provide over traditional windowing systems?

Question: What is the Collection interface?

Question: What modifiers can be used with a local inner class?

Question: What is the difference between static and non-static variables?

Question: What is the difference between the paint() and repaint() methods?

Question: What is the purpose of the File class?

Question: Can an exception be rethrown?

Question: Which Math method is used to calculate the absolute value of a number?

Question: How does multithreading take place on a computer with a single CPU?

Question: When does the compiler supply a default constructor for a class?

Question: When is the finally clause of a try-catch-finally statement executed?

Question: Which class is the immediate superclass of the Container class?

Question: If a method is declared as protected, where may the method be accessed?

Question: How can the Checkbox class be used to create a radio button?.

Question: Which non-Unicode letter characters may be used as the first character of an identifier?

Question: What restrictions are placed on method overloading?

Question: What happens when you invoke a thread's interrupt method while it is sleeping or waiting?

Question: What is casting?

Question: What is the return type of a program's main() method?

Question: Name four Container classes.

Question: What is the difference between a Choice and a List?

Question: What class of exceptions are generated by the Java run-time system?

Question: What class allows you to read objects directly from a stream?

Question: What is the difference between a field variable and a local variable?

Question: Under what conditions is an object's finalize() method invoked by the garbage collector?

Question: How are this() and super() used with constructors?

Question: What is the relationship between a method's throws clause and the exceptions that can be thrown during the method's execution?

Question: What is the difference between the JDK 1.02 event model and the event-delegation model introduced with JDK 1.1?

Question: How is it possible for two String objects with identical values not to be equal under the == operator?

Question: Why are the methods of the Math class static?

Question: What Checkbox method allows you to tell if a Checkbox is checked?

Question: What state is a thread in when it is executing?

Question: What are the legal operands of the instance of operator?

Question: How are the elements of a GridLayout organized?

Question: What an I/O filter?

Question: If an object is garbage collected, can it become reachable again?

Question: What is the Set interface?

Question: What classes of exceptions may be thrown by a throw statement?

Question: What are E and PI?

Question: Are true and false keywords?

Question: What is a void return type?

Question: What is the purpose of the enableEvents() method?

Question: What is the difference between the File and RandomAccessFile classes?

Question: What happens when you add a double value to a String?

Question: What is your platform's default character encoding?

Question: Which package is always imported by default?

Question: What interface must an object implement before it can be written to a stream as an object?

Question: How are this and super used?

Question: What is the purpose of garbage collection?

Question: What is a compilation unit?

Question: What interface is extended by AWT event listeners?

Question: What restrictions are placed on method overriding?

Question: How can a dead thread be restarted?

Question: What happens if an exception is not caught?

Question: What is a layout manager?

Question: Which arithmetic operations can result in the throwing of an ArithmeticException?

Question: What are three ways in which a thread can enter the waiting state?

Question: Can an abstract class be final?

Question: What is the ResourceBundle class?

Question: What happens if a try-catch-finally statement does not have a catch clause to handle an exception that is thrown within the body of the try statement?

Question: What is numeric promotion?

Question: What is the difference between a Scrollbar and a ScrollPane?

Question: What is the difference between a public and a non-public class?

Question: To what value is a variable of the boolean type automatically initialized?

Question: Can try statements be nested?

Question: What is the difference between the prefix and postfix forms of the ++ operator?

Question: What is the purpose of a statement block?

Question: What is a Java package and how is it used?

Question: What modifiers may be used with a top-level class?

Question: What are the Object and Class classes used for?

Question: How does a try statement determine which catch clause should be used to handle an exception?

Question: Can an unreachable object become reachable again?

Question: When is an object subject to garbage collection?

Question: What method must be implemented by all threads?

Question: What methods are used to get and set the text label displayed by a Button object?

Question: Which Component subclass is used for drawing and painting?

Question: What are synchronized methods and synchronized statements?

Question: What are the two basic ways in which classes that can be run as threads may be defined?

Question: What are the problems faced by Java programmers who don't use layout managers?

Question: What is the difference between an if statement and a switch statement?

Question: What happens when you add a double value to a String?

Question: What is the List interface?

Question: Why do we need public static void main(String args[]) method in

Question: What is the difference between an Interface and an Abstract class

Question: Explain serialization

Question: What are the rules of serialization

Question: What is difference between error and exception

Question: What do you mean by object oreiented programming

Question: What are 4 pillars of object oreinted programming

Question: Difference between procedural and object oreinted language

Question: What is the difference between constructor and method

Question: What is the difference between parameters and arguments

Question: What is reflection in java