In java global variable are not used because

[jacob deiter]

In java global variable are not used because

“The global variables breaks the referential transparency”

can anyone explain what is "referential transparency”

[Vijitha Kumara]

WikiPedia has a good explanation.

[Monu Tripathi]

jacob deiter wrote:In java global variable are not used because ....

Though a global variable(one which is not enclosed in any function or class) is hard/impossible to define in Java you can always create a properly scoped, shared variable using a public class and a public static member.

public class Global{
      public static int sharedVariable = 10;
}

I am not sure of the exact reason why global variables were excluded from Java; but IMO global variables makes understanding and maintenance of your programs difficult. The variables on which your logic depends are scattered and open for modifications. One of the features of Object Oriented programming is to keep data and the functions that operate on the data together (to achieve high degree of cohesion); global variables kind of defeats this, doesn't it?

I neither know what referential transparency means nor am I sure if my reasoning is correct; just wanted to give it a shot though

Cheers!

[Campbell Ritchie]

Monu Tripathi wrote:. . .

public class Global{
      public static int sharedVariable = 10;
}

I am not sure of the exact reason why global variables were excluded from Java; but IMO global variables makes understanding and maintenance of your programs difficult. . . . .

You mean public static final int . . . surely?

You said yourself global variables make understanding and maintenance difficult; I am sure that is why they were excluded. Also they are error-prone, and are not associated with objects, and are therefore not object-oriented programming. The only instance where a global value can be safe is where it is used as a constant. Hence "final".

[Monu Tripathi]

Campbell Ritchie wrote:You mean public static final int . . . surely?
......
......
The only instance where a global value can be safe is where it is used as a constant. Hence "final".

In C, global variables aren't necessarily constants; I was trying to emulate that aspect in my Java code. That said, I agree with you in that such global variables should be constants(therefore, final) for safety.

[Campbell Ritchie]