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Java Array Comparison
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Java Array Comparison

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Questions and Answers

What is the output of the expression cities == metros?

  • null
  • false (correct)
  • Error
  • true
  • What is the purpose of the Arrays.equals() method?

  • To compare array contents (correct)
  • To sort array elements
  • To compare array references
  • To convert an array to a string
  • Why does the code class MyStringDemo extends String {} not compile?

  • The String class is final (correct)
  • The String class is an interface
  • The String class is abstract
  • The String class is not a class
  • What is the difference between cities == capitals and cities.equals(capitals)?

    <p><code>==</code> checks for reference equality, while <code>.equals()</code> checks for content equality</p> Signup and view all the answers

    What is the output of the expression cities.equals(metros)?

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

    Why is Arrays.equals(cities, metros) necessary?

    <p>To compare array contents</p> Signup and view all the answers

    What is the purpose of the == operator when comparing arrays?

    <p>To compare array references</p> Signup and view all the answers

    What happens when you try to compile the code class MyStringDemo extends String {}?

    <p>The code does not compile because the String class is final</p> Signup and view all the answers

    If a class implements two interfaces with a default method having the same name and signature but different implementations, what will happen?

    <p>A conflict will arise due to ambiguity</p> Signup and view all the answers

    What is the correct way to declare an interface in Java?

    <p>public abstract interface Status { public static final double PI = 3.14; }</p> Signup and view all the answers

    Can a class extend an interface in Java?

    <p>No, a class can only implement an interface in Java</p> Signup and view all the answers

    What is the correct implementation of the Insurance interface?

    <p>public abstract class Car implements Insurance { }</p> Signup and view all the answers

    What happens when a class implements two interfaces with the same default method?

    <p>A conflict will arise due to ambiguity</p> Signup and view all the answers

    What is the purpose of a default method in an interface?

    <p>To provide a default implementation of the interface method</p> Signup and view all the answers

    What is the correct way to declare a method in an interface?

    <p>public abstract void insuranceDescription(String s)</p> Signup and view all the answers

    Can an interface have a static final variable in Java?

    <p>Yes, an interface can have a static final variable</p> Signup and view all the answers

    What is the name of the parent class of Faloodeh?

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

    What is the output when a.displayName("test") is called?

    <p>test Icecream</p> Signup and view all the answers

    What is the output when b.describe("test") is called?

    <p>test Faloodeh: Faloodeh is often served alongside Persian-style dairy-based ice cream</p> Signup and view all the answers

    Which method is overridden in the Faloodeh class?

    <p>displayName() and describe()</p> Signup and view all the answers

    What is the purpose of the describe() method in the Icecream class?

    <p>To provide a description of the ice cream</p> Signup and view all the answers

    What is the purpose of the displayName() method in the Faloodeh class?

    <p>To print the name of Faloodeh</p> Signup and view all the answers

    What is the data type of the variable 'a'?

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

    What is the output when a.describe("test") is called?

    <p>test Icecream: Ice cream is a sweetened frozen food typically eaten as a snack or dessert.</p> Signup and view all the answers

    What is the primary purpose of the this() call in the Calculator (int x) constructor?

    <p>To reuse the code from the no-argument constructor.</p> Signup and view all the answers

    What would happen if the Calculator (int x, int y) constructor was called without the this(5) call?

    <p>The code would not compile.</p> Signup and view all the answers

    What would be the output of the Calculator class when running the main method?

    <p>Basic arithmetic operation, 5 is the only operand supplied, Two operands supplied are multiplied and the resultant is 80.</p> Signup and view all the answers

    Which of the following statements about the Calculator class is true?

    <p>The <code>Calculator</code> class has a default constructor that is not explicitly defined.</p> Signup and view all the answers

    What is the purpose of the System.out.println statements in the Calculator constructors?

    <p>To indicate the number of operands supplied to the constructor.</p> Signup and view all the answers

    Which of the following is a characteristic of the Calculator class constructors?

    <p>They are all chained to each other using the <code>this()</code> call.</p> Signup and view all the answers

    What is a characteristic of an interface in Java?

    <p>An interface can contain public, static, final fields and default and static methods with bodies.</p> Signup and view all the answers

    Can a class implement multiple interfaces?

    <p>Yes, a class can implement multiple interfaces.</p> Signup and view all the answers

    What is true about interfaces and classes?

    <p>Many classes can implement the same interface.</p> Signup and view all the answers

    What is not true about interfaces?

    <p>An instance of an interface can be created.</p> Signup and view all the answers

    What is a benefit of using interfaces?

    <p>They enable polymorphism in Java programs.</p> Signup and view all the answers

    How do classes interact with interfaces?

    <p>A class can implement an interface.</p> Signup and view all the answers

    What is a characteristic of an abstract class?

    <p>It can extend another abstract class.</p> Signup and view all the answers

    What is true about multiple interfaces?

    <p>Many classes can implement the same interface.</p> Signup and view all the answers

    Study Notes

    Java Programming

    Arrays and Equality

    • In Java, == checks for reference equality, not content equality.
    • equals() method is used to compare the contents of two arrays.
    • Arrays.equals() method is used to compare the contents of two arrays.

    Inheritance and Interfaces

    • A class cannot extend a final class.
    • A class can implement multiple interfaces.
    • Many classes can implement the same interface.
    • An interface can contain public, static, final fields (i.e., constants), default and static methods with bodies.
    • An instance of an interface cannot be created.

    Method Overriding and Hiding

    • If a class implements two interfaces and they both have a default method with the same name and signature but different implementations, a conflict will arise because the compiler will not be able to link a method call due to ambiguity.
    • A public, static, final method in a superclass cannot be overridden by a subclass.

    Class and Interface Definitions

    • An interface can contain public, static, final fields (i.e., constants), default and static methods with bodies.
    • A class can implement multiple interfaces.
    • Many classes can implement the same interface.

    Object-Oriented Programming

    • Polymorphism: a class can take many forms.
    • A subclass can override methods of its superclass.
    • A subclass can hide methods of its superclass.

    Constructors and Inheritance

    • A subclass can call a constructor of its superclass using this() or super().
    • A constructor of a subclass can call a constructor of its superclass with arguments.

    Java Syntax and Semantics

    • A Java program can have multiple classes, but only one public class.
    • A Java class can have multiple constructors.
    • A Java constructor can have arguments.
    • A Java method can have variable arguments (varargs).

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    Description

    This quiz tests understanding of array comparison in Java, specifically whether two arrays are equal or not.

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