4. Java OOP. 6. Inner Classes

Июль 29, 2022

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4. Java OOP. 6. Inner Classes

Содержание

2. Nested Classes (1 of 2) A nested class is a class defined within another class: class
3. Nested Classes (2 of 2) A nested class is a member of its enclosing class Non-static
4. Why Use Nested Classes? It is a way of logically grouping classes that are only used
5. Static Nested Classes (1 of 2) A static nested class is associated with its outer class
6. Static Nested Classes (2 of 2) Static nested classes are accessed using the enclosing class name:
7. Inner Classes (1 of 2) An inner class has direct access to that object's methods and
8. Inner Classes (2 of 2) To instantiate an inner class, you must first instantiate the outer
9. Local Inner Classes Inner classes can be created inside code blocks, typically inside the body of
10. Anonymous Classes Anonymous classes combine the process of definition and instantiation into a single step As
11. Anonymous Class Example I new Thread(new Runnable() { public void run() { ... } }).start(); *
12. Anonymous Class Example II JFrame frame = new JFrame("AnonimDemo2"); frame.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e)
13. Anonymous Classes Use For creating objects on the fly in contexts such as: the value in
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Слайд 2

Nested Classes (1 of 2)
A nested class is a class defined

within another class:
class OuterClass {
...
class NestedClass {
...
}
}

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Слайд 3

Nested Classes (2 of 2)
A nested class is a member of

its enclosing class
Non-static nested classes (inner classes) have access to other members of the enclosing class, even if they are declared private
Static nested classes do not have access to other instance members of the enclosing class

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Слайд 4

Why Use Nested Classes?
It is a way of logically grouping classes

that are only used in one place.
It increases encapsulation.
Nested classes can lead to more readable and maintainable code (places the code closer to where it is used)

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Слайд 5

Static Nested Classes (1 of 2)
A static nested class is associated

with its outer class
Like static class methods, a static nested class cannot refer directly to instance variables or methods defined in its enclosing class - it can use them only through an object reference

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Слайд 6

Static Nested Classes (2 of 2)
Static nested classes are accessed using

the enclosing class name:
OuterClass.StaticNestedClass
To create an object for the static nested class, use this syntax:
OuterClass.StaticNestedClass nestedObject =
new OuterClass.StaticNestedClass();

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Слайд 7

Inner Classes (1 of 2)
An inner class has direct access to

that object's methods and fields
It cannot define any static members itself
Objects that are instances of an inner class exist within an instance of the outer class

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Слайд 8

Inner Classes (2 of 2)
To instantiate an inner class, you must

first instantiate the outer class. Then, create the inner object within the outer object with this syntax:
outerClass.InnerClass innerObject = outerObject.new InnerClass();

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Слайд 9

Local Inner Classes
Inner classes can be created inside code blocks, typically

inside the body of a method
A local inner class cannot have an access specifier
It does have access to the final variables in the current code block and all the members of the enclosing class

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Слайд 10

Anonymous Classes
Anonymous classes combine the process of definition and instantiation into

a single step
As these classes do not have a name, an instance of the class can only be created together with the definition

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Слайд 11

Anonymous Class Example I
new Thread(new Runnable() {
public void run()

{
...
}
}).start();

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Слайд 12

Anonymous Class Example II
JFrame frame = new JFrame("AnonimDemo2");
frame.addWindowListener(new WindowAdapter() {

public void windowClosing(WindowEvent e) {
System.exit(0);
}
});

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Слайд 13

Anonymous Classes Use
For creating objects on the fly in contexts such

as:
the value in a return statement
an argument in a method call
in initialization of variables
to implement event listeners in GUI-based applications

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