Questions and Answers
Nested classes that are declared static are called?
static nested classes
Non-static nested classes are called?
inner classes
A nested class is a member of its enclosing class.
True
Non-static nested classes (inner classes) have access to other members of the enclosing class, even if they are declared private.
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Static nested classes do not have access to other members of the enclosing class.
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A nested class can be declared private, public, protected, or package private.
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Outer classes can only be declared public or package private.
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Why use nested classes?
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As with class methods and variables, a static nested class is associated with its outer class.
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Static nested classes are accessed using the?
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Create an object for the static nested class.
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An inner class is associated with an instance of its enclosing class and has direct access to that object's methods and fields.
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An inner class is associated with an instance; it cannot define any static members itself.
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Instantiate an inner class.
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To refer to the member variable of the inner class, use the keyword this to represent the enclosing scope.
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Synthetic constructs enable Java compilers to implement new Java language features without changes to the JVM.
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Study Notes
Nested Classes Overview
- Static nested classes are defined within an enclosing class and do not have access to instance members of the enclosing class directly.
- Non-static nested classes are referred to as inner classes, which can access both instance and static members of the enclosing class, including private members.
- A nested class is inherently a member of its enclosing class.
Access and Visibility
- Inner classes possess direct access to the instance variables and methods of their enclosing class.
- Static nested classes lack direct access to instance members and must refer to them using an object reference.
- Both static and non-static nested classes can be declared with access modifiers: public, private, protected, or package-private.
- Outer classes can solely be defined as public or package-private.
Benefits of Using Nested Classes
- Logical grouping of classes that are exclusively utilized by one another increases organization within the codebase.
- Enhances encapsulation by allowing a nested class to access private members of its enclosing class while keeping it hidden from the outside world.
- Improves readability and maintainability of code by placing related classes together, which simplifies navigation within the code.
Instantiation and Syntax
- Static nested classes are instantiated using the syntax
OuterClass.StaticNestedClass nestedObject = new OuterClass.StaticNestedClass();. - Inner classes are instantiated through an instance of the enclosing class:
OuterClass.InnerClass innerObject = outerObject.new InnerClass();.
Special Features
- Inner classes are tied to the instance of their enclosing class and can define instance and non-static members, but cannot declare static members.
- To access the enclosing class's member variables from within an inner class, the keyword
thisis used to refer to the enveloping context. - Synthetic constructs in Java help implement new features without needing alterations to the Java Virtual Machine (JVM).
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Test your knowledge on nested classes with these flashcards. Learn definitions and classifications of static nested classes and inner classes. Challenge yourself with true or false questions to reinforce your understanding.
