Newbie Questions

The most embarrassing question but always bugs me every time I read in my book.
What is a type in java?
What is the difference between a variable and an instance variable?

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Originally Posted by physalis123

What is a type in java?

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Type is simply that, the type of the variable. For example int, long, double, String, Point, Foo, Bar etc. The first three are primitive types. The last four are reference types (classes).

Quote:

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What is the difference between a variable and an instance variable?

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It depends upon where your declare them.

Code:

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class Foo {
    String name; // instance variable
    static int count; // class variable

    public void doStuff() {
        int thingy = 0; // local variable
    }
}

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An instance variable is so called because each time you create an object of that class they each get their own instance of that variable. The class variable means that it belongs to the class and not an instance. So each object you create uses the same variable. The difference is very important to understand. Lastly the local variable is local to that code block (if statement, loop or method) and cannot be used outside of that code block.

Quote:

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Originally Posted by Junky

Type is simply that, the type of the variable. For example int, long, double, String, Point, Foo, Bar etc. The first three are primitive types. The last four are reference types (classes).

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Oh I remember that, so an example sentence I am struggling with is "An object of type String is a sequence of characters." Then talks about string literals with examples ("2468") and ("I must/n go home").

Quote:

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Originally Posted by Junky

An instance variable is so called because each time you create an object of that class they each get their own instance of that variable. The class variable means that it belongs to the class and not an instance. So each object you create uses the same variable. The difference is very important to understand. Lastly the local variable is local to that code block (if statement, loop or method) and cannot be used outside of that code block.

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to summarize, instance variable is a duplicated variable every time the same class is made?

Class variable is a variable only made once but used by classes in need?

local variable is found and used in a certain code block.

how to superclass and subclass work for these variables? How do you tell them apart since variables don't have headers.

Quote:

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Originally Posted by physalis123

how to superclass and subclass work for these variables? How do you tell them apart since variables don't have headers.

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It depends upon the access modifier. Public and protected variables are inherited. Private variables are not. I have no idea what you mean by headers.

Quote:

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Originally Posted by Junky

I have no idea what you mean by headers.

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I sorta meant like method headers and variables don't have those. How do you tell the variables apart.

Quote:

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Originally Posted by physalis123

How do you tell the variables apart.

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What variables are you talking about?

nevermind I got my answer thanks for the help.