Java Wrapper Classes Flashcards

Questions and Answers

What is a wrapper class?

A class used for string manipulation

A class that only works with integers

A class that provides constants and methods for working with primitive types (correct)

A class that cannot be changed

What does the Integer wrapper class do?

It wraps a value of the primitive type int in an object.

What does the Double wrapper class do?

It wraps a value of the primitive type double in an object.

What is a class constant?

A named value that cannot be changed and can be accessed anywhere in the class. Signup and view all the answers

What is Integer.MIN_VALUE?

A constant that holds the smallest value for the int data type, which is -2^31. Signup and view all the answers

What is Integer.MAX_VALUE?

A constant that holds the largest value for the int data type, which is 2^31 - 1. Signup and view all the answers

What does the intValue() method do?

It returns the value of this integer as an int. Signup and view all the answers

What is underflow?

The result of a calculation that is too small to be represented using the available number of bits. Signup and view all the answers

What is overflow?

An error that results when the number of bits is not enough to hold the number. Signup and view all the answers

What is autoboxing?

Automatic conversion between reference and primitive types. Signup and view all the answers

What is unboxing?

Convert an object to a value type. Signup and view all the answers

Study Notes

Wrapper Classes Overview

Wrapper classes are found in the java.lang package and facilitate working with primitive types by providing constants and methods.

Integer Wrapper Class

The Integer class encapsulates the primitive type int, allowing it to be treated as an object.
Contains a single int field, enabling object-oriented functionalities.

Double Wrapper Class

The Double class encapsulates the primitive type double, allowing it to be treated as an object.
Contains a single double field, enabling object-oriented functionalities similar to the Integer class.

Class Constants

Constants are immutable values defined at the class level and can be accessed throughout the class without modification.

Integer Constants

Integer.MIN_VALUE: Represents the smallest integer value, which is -2^31.
Integer.MAX_VALUE: Represents the largest integer value, which is 2^31 - 1.

Integer Methods

intValue(): Method that retrieves the int value from an Integer object.

Underflow and Overflow

Underflow occurs when calculations produce a result that is too small for the available bit representation.
Overflow occurs when calculations result in a value too large for the bit representation, akin to a car's odometer exceeding its limit.

Autoboxing and Unboxing

Autoboxing refers to the automatic conversion process between primitive types and their corresponding wrapper class types.
Unboxing is the process of converting a wrapped object back into its corresponding primitive type.

Description

This quiz features flashcards focused on Java wrapper classes, specifically Integer and Double. You'll learn about the definitions and uses of these classes in the java.lang package, helping you understand how they relate to primitive types. Test your knowledge and improve your understanding of these important Java concepts.