|
|
Java provides the super keyword that enables a subclass to refer to its superclass. The super keyword is used to access: superclass constructors superclass methods and variables Consider a Java application, which consists of multiple classes. The subclass in the application needs to reuse the constructor of the superclass. In this application, super keyword is used as [...]
David Johnson is the owner of Safest Software Co. that deals in buying and selling of hardware and software computer products. Don Allen, an employee of the Safest Software Co. is assigned the task to develop a Java application to keep track of the inventory of the computer hardware and software products. The application consists [...]
In addition to the built-in exceptions, you can create customized exception as per the application requirements. Each application that you create might have specific constraints. For example, in case of a train reservation application, a passenger must specify the destination. Also, a ticket has to be bought for a passenger who is above three years [...]
Java Tutorial : Throwing An Exception – Part 1 Printing a Stack Trace When an exception is caught, you can find out the method or the line of the code where the exception is raised by using the printStackTrace() method. You can call the printStackTrace() method for printing the stack trace. The objects of the [...]
You can throw an exception explicitly using the throw statement. For example, you need to throw an exception when a user enters a wrong loginID or password. The throws clause is used to list the types of exceptions that can be thrown during the execution of a method in a program. Using the throw Statement [...]
Handling the Unreachable Code Problem The multiple catch blocks generate unreachable code error. If the first catch block contains the Exception class object then the subsequent catch blocks are never executed. The Exception class being the superclass of all the exception classes catches various types of exceptions. The Java compiler gives an error stating that [...]
When an unexpected error occurs in a method, Java creates an object of the type Exception. After creating the Exception object, Java sends it to the program by throwing the exception. The Exception object contains information about the type of error and the state of the program when the exception occurred. You need to handle [...]
The built-in exceptions in Java are categorized on the basis of whether the exception is handled by the Java compiler or not. Java consists of the following categories of built-in exceptions: Checked Exceptions Unchecked Exceptions Checked Exceptions Checked exceptions are the objects of the Exception class or any of its subclasses excluding the Runtime Exception [...]
Exception Handling To handle exceptions, the Java run-time system searches for an exception-handler. In Java, a catch statement is an exception-handler that is used to handle an exception. The search for an exception-handler begins with the method in which the exception is raised. If no appropriate exception-handler is found, the Java run-time system searches the [...]
The term exception in Java indicates an exceptional event. It can be defined as an abnormal event that occurs during program execution and disrupts the normal flow of instructions. The abnormal event can also be an error in the program. Errors in a Java program are categorized into two groups: compile-time errors and run-time errors. [...]
Inheritance is the concept of extending data members and methods of a superclass in a subclass. You can derive data members and methods from a single superclass that is a subclass of another superclass. Java does not support multiple inheritance directly. You can use the concept of method overriding to override the superclass method with [...]
There might be cases where you might need to inherit the features of more than one class. But Java does not support multiple inheritance. However, you can simulate multiple inheritance in Java by using interfaces. An interface is a collection of methods and data members that can be implemented by any number of classes residing [...]
When you extend the functionality of a class, the subclass inherits the data members and methods from the superclass. For example, if the superclass has a show() method, which displays the value of the superclass, the subclass inherits the show() method from the superclass. When you call this method from an object of the subclass, [...]
In multilevel inheritance, a subclass inherits the properties of another subclass. For example, Class A is a superclass for the Class B; and Class B is a superclass for the subclass, Class C. You can include any number of levels in multilevel inheritance. The following syntax shows how to implement multilevel inheritance: class A { [...]
In the last article we saw the inheritance in java. The following syntax shows how to implement single level inheritance: class A { //body of Class A } class B extends A { //body of Class B } class C extends A { //body of Class C } In the preceding syntax, the extends keyword [...]
