You manipulate objects with handles

with
handles

Each

programming language has its own means of manipulating data. Sometimes the

programmer must constantly be aware of what type of manipulation is going on.

Are you manipulating the object directly or are you dealing with some kind of

indirect representation (a pointer in C or C++) that must be treated with a

special syntax?

All

this is simplified in Java. You treat everything as an object, so there is a

single consistent syntax that you use everywhere. Although you

everything

as an object, the identifier you manipulate is actually a “handle”

to an object. (You might see this called a

or even a pointer in other discussions of Java.) You might imagine this scene

as a television (the object) with your remote control (the handle). As long as

you’re holding this handle, you have a connection to the television, but

when someone says “change the channel” or “lower the

volume,” what you’re manipulating is the handle, which in turn

modifies the object. If you want to move around the room and still control the

television, you take the remote/handle with you, not the television.

Also,

the remote control can stand on its own, with no television. That is, just

because you have a handle doesn’t mean there’s necessarily an

object connected to it. So if you want to hold a word or sentence, you create a

handle:

But

here you’ve created

the handle, not an object. If you decided to send a message to

at this point, you’ll get an error (at run-time) because

isn’t actually attached to anything (there’s no television). A

safer practice, then, is always to initialize a handle when you create it:

However,

this uses a special case: strings can be initialized with quoted text.

Normally, you must use a more general type of initialization for objects.

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