Java Programming: Input, Operators, and OOP Concepts
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Questions and Answers

Which of the following is the correct expansion of the UML acronym?

  • User Management Language
  • Unified Modular Language
  • Universal Modeling Language
  • Unified Modeling Language (correct)

In a UML class diagram, if a member is marked with a '+', what does this signify about its accessibility?

  • Private member
  • Public member (correct)
  • Protected member
  • Default access

Which item is typically excluded from a standard UML class diagram?

  • Class Name
  • Loops (correct)
  • Methods
  • Attributes

Which Java package is implicitly included in every Java source file, providing fundamental classes and interfaces?

<p>java.lang (A)</p> Signup and view all the answers

Given the Java code "Hello".charAt(1), what character will be returned?

<p>'e' (D)</p> Signup and view all the answers

What is the data type of the returned result when using the Math.pow(2, 3) method in Java?

<p>8.0 (C)</p> Signup and view all the answers

If you need to encapsulate a primitive boolean value as an object in Java, which wrapper class should you use?

<p>Boolean (A)</p> Signup and view all the answers

Which Javadoc tag is used to document the parameters that a method accepts?

<p>@param (A)</p> Signup and view all the answers

Consider this code snippet: int x = 7; int y = x % 3;. What value will y hold after execution?

<p>1 (C)</p> Signup and view all the answers

Given the code: int age = 20; if (age >= 18) { System.out.println("Eligible"); } else { System.out.println("Not Eligible"); } What is the output?

<p>Eligible (D)</p> Signup and view all the answers

Which of the following statements is most accurate about the break keyword's role in a switch statement?

<p>It's necessary to prevent 'fall-through' to the next case. (D)</p> Signup and view all the answers

Suppose you have a class named Dog. Which line of code correctly creates an instance of Dog named myDog?

<p><code>Dog myDog = new Dog();</code> (D)</p> Signup and view all the answers

Why is encapsulation considered a fundamental principle of object-oriented programming?

<p>It bundles data and methods that operate on that data, protecting the data from outside interference. (D)</p> Signup and view all the answers

What is the primary responsibility of a constructor method within a Java class?

<p>To initialize the object's state when it is created. (D)</p> Signup and view all the answers

Which of these access modifiers provides the highest level of restriction, limiting access only to the declaring class?

<p>private (B)</p> Signup and view all the answers

You're tasked with designing an online store. One class is Product, and another is ShoppingCart. What is the most likely relationship between these two classes?

<p>Association: <code>ShoppingCart</code> uses <code>Product</code>. (D)</p> Signup and view all the answers

Flashcards

Taking integer input in Java

Use Scanner class: Scanner input = new Scanner(System.in); int num = input.nextInt();

Output of x += 5

The variable x starts as 10, and x += 5 means x = x + 5, resulting in 15.

Modulus operator (%)

In Java, % finds the remainder after division, not the quotient.

If-Else statement output

The output will be 'Greater' if a is greater than 5; otherwise, 'Smaller'.

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Switch statement requirement

The switch statement requires 'break' after each case to prevent fall-through and ensure proper execution.

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Object in Java

An object is an instance of a class, representing real-world entities with attributes and methods.

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Creating an object

Use the keyword 'new' to create an object in Java, e.g., MyClass obj = new MyClass();

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Encapsulation in Java

Encapsulation is hiding data by using private variables in classes to control access.

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Unified Modeling Language (UML)

A standardized modeling language used to visualize the design of a system.

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  • symbol in UML

Indicates a public member in a UML class diagram.

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Default package in Java programs

The java.lang package which is automatically imported in every Java program.

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String.charAt() method

Returns the character at a specified index in a string.

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Math.pow() method

Calculates the value of a number raised to a power.

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Wrapper class for boolean

The Boolean class in Java encapsulates the primitive boolean type.

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Javadoc @param tag

Used to document parameters of a method in Javadoc.

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Default value of int array

The default value for each element in an int array is 0.

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Study Notes

Java Programming Study Notes (Weeks 2-6)

  • Input: Use Scanner to read user input.
    • Correct syntax: Scanner input = new Scanner(System.in); int num = input.nextInt();
  • Arithmetic Operators:
    • +=: Adds the value on the right to the variable.
    • Modulus (%): Returns the remainder of a division.
  • Control Flow (if-else):
    • if statements execute code based on a boolean condition.
    • else block executes if the if condition is false.
  • Control Flow (switch):
    • Use break after each case in a switch statement to prevent fall-through.
  • Object-Oriented Programming (OOP):
    • Object: An instance of a class.
    • Constructor: Initializes an object.
    • Encapsulation: Hiding data using private variables to control access.
  • UML Class Diagrams:
    • UML: Unified Modeling Language. Used for visual representation of software systems.
    • Public member: Designated by a plus sign (+) in UML diagrams.
    • Class diagram Components: Includes class name, attributes, and methods, but NOT loops.
  • Packages:
    • java.lang is automatically imported.
  • String Class:
    • charAt(index) returns the character at a specified index. Example: Hello.charAt(1) returns 'e'.
  • Math Class:
    • Math.pow(base, exponent) raises the base to the exponent power. Example: Math.pow(2,3) = 8.0
  • Wrapper Classes:
    • Boolean for boolean, Integer for integers, etc.
  • Javadoc:
    • @param (Javadoc tag) describes method parameters.
  • Arrays:
    • Default value: int arrays are initialized with 0 values.
    • Length: arr.length gives the size. Example int[] arr = new int[5], arr.length = 5
    • Enhanced for loop: Can't modify the array elements within the loop.
    • Array Passing: The original array reference is used, modifying it inside the method affects the original array.
  • ArrayList:
    • Use add() method to add elements.
  • Sorting Arrays: Use the Arrays class for sorting arrays.

Key Concepts

  • Scanner: Used for taking user input.
  • if-else: Conditional statements.
  • switch: Multiple conditional checks.
  • Objects, Classes, Encapsulation: Object-oriented principles.
  • UML: Visual representation of software structure.
  • Packages: Organize related classes.
  • String class: Manage strings.
  • Math class: Perform mathematical operations.
  • Wrapper classes: Convert between primitive and object types.
  • Javadoc: Documentation comments for code.
  • Arrays: Store collections of data.
  • ArrayList: Dynamically sized collections.

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Description

Explore Java programming concepts including Scanner input, arithmetic operators, and control flow statements. Understand object-oriented programming principles with objects, constructors, and encapsulation. Covers UML class diagrams for software system visualization.

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