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Questions and Answers
What determines which other classes have access to a class?
What determines which other classes have access to a class?
Access Modifier
What keyword allows us to add to existing classes?
What keyword allows us to add to existing classes?
extends OldClassName
What keyword indicates a class will provide code for each item specified in an interface?
What keyword indicates a class will provide code for each item specified in an interface?
implements InterfaceName
What are primitive data and objects that contain the state of an object called?
What are primitive data and objects that contain the state of an object called?
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What provides the code needed to create and initialize an object as defined by its class?
What provides the code needed to create and initialize an object as defined by its class?
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What method type does the internal work for a class that users don’t need to worry about?
What method type does the internal work for a class that users don’t need to worry about?
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What are the programming interfaces of a class to other classes called?
What are the programming interfaces of a class to other classes called?
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What elements can be a class, block, method, or variable that members do not need an object to access?
What elements can be a class, block, method, or variable that members do not need an object to access?
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What is the major executable part of a class or program that is static and has a void return type?
What is the major executable part of a class or program that is static and has a void return type?
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What is used to initialize static fields of a class, executing once when the class is loaded?
What is used to initialize static fields of a class, executing once when the class is loaded?
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Study Notes
Access Modifiers
- Defines the accessibility level of classes; includes public, private, and default.
- Public classes are accessible by any other class, while private classes can only be accessed within their enclosing class.
Inheritance (extends)
- The
extendskeyword enables a class to inherit methods and fields from an existing class. - Supports polymorphism, allowing one interface to be used for different underlying forms.
Interfaces (implements)
- The
implementskeyword specifies that a class will provide implementations for all methods in an interface. - Facilitates polymorphism through composition, enabling the class to have multiple behaviors.
Fields
- Represent the state of an object, consisting of primitive data types and objects.
- Typically marked as private to encapsulate data, except for constants which may be public.
Constructors
- Special methods for creating and initializing new object instances of a class.
- Must be invoked following the
newkeyword during object creation.
Private Methods
- Perform internal operations of a class that are not intended for user interaction or access.
- Help maintain encapsulation and prevent external interference.
Public Methods
- Serve as the interface for other classes to interact with the class.
- Ensure controlled access to private fields and methods, encapsulating the internal workings.
Static Elements
- Can include static classes, methods, variables, or blocks that belong to the class itself rather than instances.
- Shared across all instances of the class, inherently accessible without object instantiation.
Static Main Method
- A mandatory static method with a
voidreturn type that functions as the entry point of a Java application. - Responsible for initiating class testing or program execution.
Static Block
- Used to initialize static fields of a class, executed once when the class is loaded into memory.
- Can also initialize static fields that have been imported, aiding in the setup of class-level variables.
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Description
Test your knowledge of key concepts in Java class diagrams. This quiz covers fundamental terms such as access modifiers, inheritance, and interfaces. Perfect for anyone looking to strengthen their understanding of object-oriented programming in Java.
