CODEWITHSUNDEEP
javavariables
Wolfgang1337
Wolfgang1337

Reputation: 23

What's the difference between "int variable = 0;" and "int variable; variable = 0;" in Java class?

I have two versions of codes.

Version 1

Launcher.java

class Launcher {
    public static void main(String[] args) {
        LuckyNumber game;
        game = new LuckyNumber();

        game.start();
    }
}

Player.java

class Player {
    int randomNumber = 0;

    public void roll(){
        randomNumber = (int) (Math.random() * 10);
    }

}

LuckyNumber.java

class Launcher {
    public static void main(String[] args) {
        LuckyNumber game;
        game = new LuckyNumber();

        game.start();
    }
}

Version 2

Launcher.java

class Launcher {
    public static void main(String[] args) {
        LuckyNumber game;
        game = new LuckyNumber();

        game.start();
    }
}

Player.java

class Player {
    int randomNumber;
    randomNumber = 0;

    public void roll(){
        randomNumber = (int) (Math.random() * 10);
    }

}

LuckyNumber.java

class Launcher {
    public static void main(String[] args) {
        LuckyNumber game;
        game = new LuckyNumber();

        game.start();
    }
}

The first version of the code compiles without problems, but the second version of the code can not compile, and compiler shows the following errors:

.\Player.java:4: error: <identifier> expected
    randomNumber = 0;
                ^
.\Player.java:4: error: cannot find symbol
    randomNumber = 0;
    ^
  symbol:   class randomNumber
  location: class Player
2 errors

So question is why:

int variable;
variable = 0;

isn't the same as:

int variable = 0;

And what's the difference?

Upvotes: 0

Views: 1010

Answers (4)

thopaw
thopaw

Reputation: 4054

A class in Java can have members.

class Player {
    int variable = 0; // this defines a member variable within the class Player
}

But you can not put code/expressions in a class declarations body. This can only be in methods or the constructor or during the initializing of variables.

int variable;
variable = 0; // this is an expression and should be within the constructor, a method or the initialiser of the variable.

Upvotes: 0

forpas
forpas

Reputation: 164164

This is a declaration:

int variable;

and this is a declaration with initialization:

int variable = 0;

They're both valid at the class level and inside a method.
However for an already declared variable, this:

variable = 0;

is considered to be executable code and it is valid only inside a method and not at the class level.
In an IDE like IneliJ, if you write:

int variable;
variable = 0;

the ide will prompt you to merge the 2 lines to this:

int variable = 0;

because it is the same.

Upvotes: 0

ipave
ipave

Reputation: 1338

It's the same untill you write your code outside of method. You can't do like this:

class Player {
    int randomNumber;
    randomNumber = 0;

It will cause Java syntaxis error. You should read about Java properties.

Upvotes: 0

Joe C
Joe C

Reputation: 15714

The two are the same, but only when they are in a method.

In your case, initializating variables without declaring them is invalid outside of a method.

Upvotes: 3

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