Questions and Answers
What is a key advantage of using wrapper objects?
What is the purpose of inheritance?
What is an example of a class that can grow arbitrarily large?
What is a characteristic of an ArrayList?
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What is the term for automatically converting a primitive to a wrapper object?
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What is the term for automatically converting a wrapper object to a primitive?
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How do you use the BigInteger class?
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What is the purpose of encapsulation?
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What is the purpose of using the @Override annotation?
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What is the concept called when a sub-class object is treated as an instance of its super-class?
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What is one of the best practices when overriding the equals() method?
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Why does upcasting work with classes?
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Why is inheritance useful in object-oriented programming?
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What is polymorphism related to in object-oriented programming?
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What principle ensures that functions using pointers or references to base classes can use objects of derived classes without knowing it?
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What is the significance of the equals() method in Java?
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What is the result of assigning a sub-class object to a super-class reference?
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What is the purpose of upcasting?
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Why is it important to follow best practices when overriding the equals() method?
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What is an example of upcasting?
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Why is upcasting possible in object-oriented programming?
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What is the relationship between the RRSP class and the BankAccount class?
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Study Notes
String and Array Methods
- String methods belong to String objects.
- Array methods belong to the Arrays class.
ArrayList
- Follows typical object declaration syntax.
- Can add as many elements as needed, and the ArrayList grows accordingly.
- Very powerful, as the programmer is not responsible for basic behavior.
Auto-boxing and Auto-unboxing
- Auto-boxing and auto-unboxing allow primitive types to be treated as objects.
- Wrapper objects can be used like their wrapped primitives and provide advantages due to being objects, such as being members of ArrayLists.
BigInteger
- Grows arbitrarily large like a Python integer.
- Requires import java.math.*; to use.
Inheritance and Polymorphism
- Inheritance is used to create a new class based on an existing class.
- Inheritance is implemented using the "extends" keyword.
Upcasting
- Upcasting: a sub-class object can be treated as an instance of its super-class.
- This works because a sub-class can do everything its super-class can do.
- Liskov Substitution Principle: functions that use pointers or references to base classes must be able to use objects of derived classes without knowing it.
Downcasting
- No direct mention of downcasting, but it is implied as the opposite of upcasting.
Overriding and Overloading
- Overriding: a sub-class provides a specific implementation for a method already defined in its super-class.
- Overloading: multiple methods with the same name but different parameters.
- @Override annotation is used to ensure that the method is intended to override a super-class method.
Overriding equals()
- When overriding equals(), ensure that the following hold true:
- If a.equals(b), then b.equals(a) should be true.
- If a.equals(b), and b.equals(c), then a.equals(c) should be true.
- A meaningful equals method is critical, as other classes rely on it, specifically methods add() and contains() from the Collection class.
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Description
This quiz covers the basics of string and array methods in JavaScript, including their syntax and usage.