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Questions and Answers
What is the primary limitation of a local variable?
What is the primary limitation of a local variable?
- It can only be accessed with the `this` keyword.
- It can only be accessed and used within the specific method it is declared in. (correct)
- It can only be accessed by the class it is declared in.
- It cannot be modified after it is declared.
How can a class variable declared as 'private' typically be accessed within its own class?
How can a class variable declared as 'private' typically be accessed within its own class?
- By explicitly calling the variable name directly without any keyword.
- By using the `class` keyword followed by the variable name.
- By using the `global` keyword followed by the variable name.
- By using the `this` keyword followed by the variable name. (correct)
Why can declaring a sound variable as a local variable cause a sound to play repeatedly every time a program is started?
Why can declaring a sound variable as a local variable cause a sound to play repeatedly every time a program is started?
- Because a new sound object is created each time, without stopping the previous one. (correct)
- Because the sound object becomes globally accessible, overriding the local instance.
- Because the local variable prevents the sound from being stopped.
- Because local variables are not correctly managed between program restarts.
Which of the following is NOT a characteristic typically associated with a class variable compared to a local variable?
Which of the following is NOT a characteristic typically associated with a class variable compared to a local variable?
What is a critical difference in the behavior of local and class variables in object-oriented programming?
What is a critical difference in the behavior of local and class variables in object-oriented programming?
Flashcards
Local Variable
Local Variable
Variables declared within a method, accessible ONLY within that method.
Class Variable
Class Variable
Variables declared within a class, accessible by ALL methods in that class. Use the 'this' keyword to access.
Sound Issue: Local Variable
Sound Issue: Local Variable
When a program restarts, a local variable gets recreated. If it's a sound, this means a new sound plays every time.
Stopping Sound: Class Variable
Stopping Sound: Class Variable
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Importance of Local vs Class
Importance of Local vs Class
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Study Notes
Local vs Class Variables
- Local variables are declared within a method; they are only accessible and usable within that specific method.
- Class variables, also known as attributes, are declared with the
privatekeyword. They belong to the entire class and can be accessed by any method within that class using thethiskeyword. - Class variables are accessible via the
thiskeyword, as they exist throughout the class's lifespan.
Example: Local and Class Variables
- Inside the
startedmethod, a local variablegof typeGreenfootSoundis declared. gis only accessible within thestartedmethod.- To access
goutside thestartedmethod, declare it as a class variable. - After declaring
gas a class variable, access it within any method of the class usingthis.g.
Example: Sound Issue
- The sound repeatedly plays upon program restart because the sound variable (
g) is a local variable. Each run creates a new sound. - To stop the sound, stop it before a new sound is initialized.
- This problem is solved by declaring the sound variable as a class variable, allowing access to stop the sound before any new instances are made.
Key Points
- Local variables exist only within the method where they are declared.
- Class variables persist throughout the entire class's existence and are accessible by any method.
- Grasping the distinction between local and class variables is essential for object-oriented programming.
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