Java bans Global Variables

[KALLIYAN]

Hi, to all. I have just started to work on Java. I am finding it very interesting. I have earlier studied C, C++ and Visual Basics 6.0 programming languages. While studying Java I realized that Java does not supports Global Variables. What is the reason for this ? Why Java decied to not use Global Variables ?

[Praetor]

Yes its true, that Global variables are considered Bad in Java. Even I was confused when I came to know about this. There are a number of reasons for which Java does not support Global Variables. To tell you one of the reason is Adding state(Global) variables breaks referential transparency. In simple words, you can no longer can understand a statement or expression on its own.

[Katty]

Java has a very Basic concept which states "Every Variable in Java must be declared within a class." Declaring a Global variable violets the concept and hence Java has Banned Global variables. But as a C++ programmer this would be a limitation for you. The solution is keyword static which indicates that a particular variable is a class variable rather than an instance variable. This makes it very clear that there would only be one copy of the variable. It would not allow creating multiple copies of that variable for every instance of the class.

[kelfro]

Creating a Global variable will thereby allow creating a copy of that variable for each instance of the class. This in Java is considered as a limitation because you are limiting the use fo your program to one instance. Also, Global variables creates collisions in namespace. To not allow such limitation Java has done away with the concept of Global variables.

[Daren]

in JAVA you can make something global by the following ways

declare the variable as a public variable, a static variable, or a private variable.

you would declare it like so

class thisOne{
public int num;
private int number;
static int numb;

public void some method{}

and so on

the public means it can be viewed at any stage of the class
private means that it is back end only
static means it can't be changed such as if you want a number to stay absolute.