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Java Classes and Objects Flashcards
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Java Classes and Objects Flashcards

Created by
@EasygoingAgate6318

Questions and Answers

What does OOP stand for?

  • Object-Orienting Programming
  • Object-Oriented Programming (correct)
  • Object-Ordered Programming
  • Object-Operations Programming

    • What are attributes in object-oriented programming?

    Characteristics in an object.

    What does behavior refer to in the context of objects?

    Dependent on the object type.

    What are the three dimensions in object-oriented programming?

    <p>Identity, Attributes, Behavior.</p> Signup and view all the answers

    What is a class?

    <p>It describes what an object will be.</p> Signup and view all the answers

    What is the basic class syntax in Java?

    <p>public class (name class here) {</p> Signup and view all the answers

    What is a method in programming?

    <p>Synonymous for behavior.</p> Signup and view all the answers

    How do you declare a method in Java?

    <p>class Myclass { static void sayHello() { //sayHello is the method System.out.println(&quot;Hello World!&quot;) }</p> Signup and view all the answers

    What is code reuse?

    <p>Write a method once and use it multiple times.</p> Signup and view all the answers

    What is return value syntax in Java?

    <p>class MyClass { static int sum(int val1, int val2) { return val1 + val2; }</p> Signup and view all the answers

    Public access modifier means the class is accessible by any other class.

    <p>True</p> Signup and view all the answers

    What is a package in Java?

    <p>A group of similar types of classes.</p> Signup and view all the answers

    Default variables or methods are available to any other class in different packages.

    <p>False</p> Signup and view all the answers

    Protected methods and variables can be accessed by subclasses.

    <p>True</p> Signup and view all the answers

    Private variables are accessible only within the declared class.

    <p>True</p> Signup and view all the answers

    What is a getter method?

    <p>Returns value.</p> Signup and view all the answers

    What is the syntax for a getter method in Java?

    <p>public String getVariable()</p> Signup and view all the answers

    What is a setter method?

    <p>Sets value.</p> Signup and view all the answers

    What is the syntax for a setter method in Java?

    <p>public void setVariable(String something)</p> Signup and view all the answers

    What is encapsulation in programming?

    <p>Wrapping data and code as a single unit.</p> Signup and view all the answers

    What are constructors in Java?

    <p>Special methods invoked when an object is created.</p> Signup and view all the answers

    What are the two expectations for constructors?

    <ul> <li>Name must be the same as class name</li> <li>Must have no explicit return type</li> </ul> Signup and view all the answers

    Match the following types to their descriptions:

    <p>byte = 8-bit integer short = 16-bit integer int = 32-bit integer long = 64-bit integer float = Single-precision floating point double = Double-precision floating point boolean = True or false value char = Single 16-bit Unicode character</p> Signup and view all the answers

    What is a boolean type?

    <p>Returns true or false.</p> Signup and view all the answers

    What is a reference variable?

    <p>When you create an object using the constructor.</p> Signup and view all the answers

    What is the Math class in Java?

    <p>Provides predefined methods for mathematical operations.</p> Signup and view all the answers

    What does Math.abs() do?

    <p>Returns the absolute value of its parameter.</p> Signup and view all the answers

    What does Math.ceil() do?

    <p>Rounds to the nearest integer up when using double.</p> Signup and view all the answers

    What does Math.max() do?

    <p>Rounds to the nearest integer down when using double.</p> Signup and view all the answers

    What does Math.min() do?

    <p>Returns the smallest parameter.</p> Signup and view all the answers

    What does Math.pow() do?

    <p>Takes two parameters and returns the first raised to the power of the second.</p> Signup and view all the answers

    What does sqrt() calculate?

    <p>Square root.</p> Signup and view all the answers

    What does sin() calculate?

    <p>Sine.</p> Signup and view all the answers

    What does cos() calculate?

    <p>Cosine.</p> Signup and view all the answers

    What does the final keyword do?

    <p>Keeps a variable constant.</p> Signup and view all the answers

    What are packages in Java?

    <p>A group made up of similar types of classes.</p> Signup and view all the answers

    Study Notes

    Object-Oriented Programming (OOP)

    • Emphasizes the use of objects which contain data and methods.
    • Key components include attributes, behaviors, and class structures.

    Attributes and Behavior

    • Attributes are characteristics of an object, such as color.
    • Behavior refers to actions defined by the object type.

    Class Fundamentals

    • A class is a blueprint for creating objects.
    • Class definition begins with public class ClassName {.

    Methods

    • Methods represent behaviors; they encapsulate operations for an object.
    • Example method syntax: 
      static void sayHello() {
    System.out.println("Hello World!");
}

    Code Reuse

    • Methods can be written once and reused multiple times, enhancing efficiency.

    Return Values

    • Methods can return values using syntax like: 
      static int sum(int a, int b) {
    return a + b;
}
    • Return type must match the data type of the returned value.

    Access Modifiers

    • Public allows class accessibility from any class.
    • Default (no modifier) grants access within the same package.
    • Protected extends access to subclasses.
    • Private restricts access to the defining class only.

    Getters and Setters

    • Getters retrieve values, syntax example: 
      public String getVariable() {
    return variable;
}
    • Setters assign values, syntax example: 
      public void setVariable(String value) {
    this.variable = value;
}

    Encapsulation

    • Combines data (variables) and methods into a single unit to improve data security.

    Constructors

    • Special methods for initializing objects.
    • Constructors must have the same name as the class and no return type.

    Primitive Data Types

    • Includes byte, short, int, long, float, double, boolean, char.

    Boolean Data Type

    • Represents true or false values.

    Reference Variables

    • Created when instantiating an object from a class.

    Math Class Operations

    • Predefined methods for mathematical calculations, such as:
      • Math.abs(): Absolute value
      • Math.ceil(): Rounds up to the nearest integer
      • Math.max() and Math.min(): Returns the maximum or minimum of parameters
      • Math.pow(): Raises a number to a specified power

    Special Mathematical Functions

    • sqrt(): Computes the square root.
    • sin() and cos(): Compute sine and cosine, respectively.

    Final Keyword

    • Declares constants that cannot be modified after initial assignment. Example: 
      public static final double PI = 3.14;

    Packages

    • A package groups related classes and can contain sub-packages for organizing code.

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    Description

    Test your knowledge on Java's Object-Oriented Programming concepts with these flashcards. Cover essential terms like attributes, behaviors, and class characteristics. Perfect for beginners looking to solidify their understanding of OOP in Java.

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