In designing a number of classes, you may find there are some common elements among them. To extract the common and make it a class is to create a super class. The individual parts of the original classes become subclasses. In cases we do …

toString() is a special instance method that returns a string particular to the instance. Whenever the string is demanded, toString() is called and provides the string. The situation the particular string is demanded is like being argument…

8. Java: Inheritance Inheritance is to derive a class from another class. It is to create a class by making use of properties of another class. The derived class is called a subclass and the parent class is called a superclass. Constructor…

There are two ways for parameter passing between the method calling side and the called. One is called “by value” and the other is “by reference”. The former is applied to primitive data types, the latter to objects. Look at the sample pro…

Constructor is a special method which is more like an instance method than a class method, for it is related with instance. Constructor can access all of instance fields and methods and static fields and methods. However, it can run withou…

There are two kinds of member in java class. One is called static member, the other is non-static member. Static member includes static field and static method: Static members are with "static" modifier. Those are said to belong to the cla…

A java program may consist of a number of packages. A package may have a number of classes. For the time being, our program is made of only one package, which is nameless package.Access Control is to control access to a member in a class. …

In Java, a program is made of one main class and some other classes. In java application program, which we are learning now, program execution starts with the main method of the main class. As we have already studied, there are some basic …

Java is a relatively new type of computer programming language having features at least as 1.It is an object oriented language. “Object oriented language” means that the program written by the language is based on modules called objects. T…