Java Referencing vs creating instance

I am relatively new to Java, I want to understand the difference b/w referencing and instantiating.

I know if I have a class Bike and at some point use Bike bk = new Bike(); that would be creating an instance. But how about creating a reference? what does that mean?

thanks.

In your example bk is your reference. It references an object (Bike) (thats not 100% correct - bk is more a variable that saves the reference, but for understanding its ok i think :))

Nope, bk is a reference, the value of which is the location of the object created by 'new Bike()'.

If I point (reference) an already existing bike I'm not creating a bike; if I create a bike and then point at it I'm effectively protecting the bike against the evil garbage collector; e.g.

Code:

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Bike a= new Bike(); // create a bike and point at it
Bike b= a; // point to an existing bike
a= null; // b still points at the bike
b= null; // now the bike can be collected

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kind regards,

Jos

Thanks guys.

Quote:

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Originally Posted by Tolls

Nope, bk is a reference, the value of which is the location of the object created by 'new Bike()'.

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I thought bk is an instance of Bike. If bk is a reference of bike, does that mean I can use them interchangeably?

The non-primitive variables we use in code are references to objects on the heap.
So 'bk' is a reference to the Bike object created by 'new Bike()'.

In the same way that:

Code:

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int x = 0;

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The variable 'x' is an int primitive.

I understand. Then what's an instance?

Quote:

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Originally Posted by garnaout

I understand. Then what's an instance?

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Anything you create with the 'new' operator is an instance of some class; in your example that Bike is an instance of your Bike class.

kind regards,

Jos

thanks guys