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)`?

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

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

false Signup and view all the answers

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

To compare array contents Signup and view all the answers

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

To compare array references Signup and view all the answers

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

The code does not compile because the String class is final 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?

A conflict will arise due to ambiguity Signup and view all the answers

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

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

Can a class extend an interface in Java?

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

What is the correct implementation of the Insurance interface?

public abstract class Car implements Insurance { } Signup and view all the answers

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

A conflict will arise due to ambiguity Signup and view all the answers

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

To provide a default implementation of the interface method Signup and view all the answers

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

public abstract void insuranceDescription(String s) Signup and view all the answers

Can an interface have a static final variable in Java?

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

What is the name of the parent class of Faloodeh?

Icecream Signup and view all the answers

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

test Icecream Signup and view all the answers

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

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

Which method is overridden in the Faloodeh class?

displayName() and describe() Signup and view all the answers

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

To provide a description of the ice cream Signup and view all the answers

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

To print the name of Faloodeh Signup and view all the answers

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

Icecream Signup and view all the answers

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

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

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

To reuse the code from the no-argument constructor. Signup and view all the answers

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

The code would not compile. Signup and view all the answers

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

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

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

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

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

To indicate the number of operands supplied to the constructor. Signup and view all the answers

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

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

What is a characteristic of an interface in Java?

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

Can a class implement multiple interfaces?

Yes, a class can implement multiple interfaces. Signup and view all the answers

What is true about interfaces and classes?

Many classes can implement the same interface. Signup and view all the answers

What is not true about interfaces?

An instance of an interface can be created. Signup and view all the answers

What is a benefit of using interfaces?

They enable polymorphism in Java programs. Signup and view all the answers

How do classes interact with interfaces?

A class can implement an interface. Signup and view all the answers

What is a characteristic of an abstract class?

It can extend another abstract class. Signup and view all the answers

What is true about multiple interfaces?

Many classes can implement the same interface. 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.