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Index › Programming Questions & Help › Syntax Questions › Noob question about initializing variables
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Noob question about initializing variables (Read 250 times)
Phattee
Noob question about initializing variables
Mar 2nd, 2009, 7:08pm  
Quote:
int[] x = new int[100];
int count;

void setup() {
 size(100, 100);
}

void draw() {
 x[count] = mouseX;
 count++;
 if (count == x.length) {
   x = expand(x);
   println(x.length);
 }
}



Hello, I was working on the preceding example and noticed that the variable "count" is declared but no value is assigned to it, yet the program still works fine. So if no value is specifically assigned to a variable, is it automatically set to zero?

I apologize if I've used any terminology incorrectly.
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JohnG
Re: Noob question about initializing variables
Reply #1 - Mar 2nd, 2009, 7:38pm  
The primitive types, float, int, boolean, byte etc all have default values. Object types however need to be explicitly initialised.
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Phattee
Re: Noob question about initializing variables
Reply #2 - Mar 2nd, 2009, 7:43pm  
Thank you!
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PhiLho 
Re: Noob question about initializing variables
Reply #3 - Mar 2nd, 2009, 10:46pm  
You have to distinguish variables local to a function (method) and at class level (or "global" at Processing sketch level).

Local variables doesn't have a default value: Java compiler will complain if you use them before setting them.

Class level variables (or fields, or members) always have a default value: 0 or 0.0 for numbers, false for booleans, null for objects, etc.

So there is no need to set these variables to default values, it is even seen as bad practice (as it is redundant: they will be initialized twice).
But of course, you can set them to another value at declaration time (although most objects should be init in setup(), because at this time you know stuff like data folder path, width and height, etc.).
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« Last Edit: Mar 3rd, 2009, 6:10pm by PhiLho  »  
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Phattee
Re: Noob question about initializing variables
Reply #4 - Mar 2nd, 2009, 11:05pm  
PhiLho  wrote on Mar 2nd, 2009, 10:46pm:
Note to what JohnG added: what he wrote is correct for local variables, and Java compiler will complain if you don't initialize objects. It is still true for member variables (ie. fields, variables declared at class level) except that objects there are always initialized at null. So there is no need to set these variables to default values,it is even seen as bad practice.


Cool thanks! Very useful info.
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PhiLho 
Re: Noob question about initializing variables
Reply #5 - Mar 3rd, 2009, 6:10pm  
Argh! Actually the info you quote is incorrect... Sad
I edited my message to give better information!
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