Kotlin vs. Java Syntax Comparison

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Questions and Answers

Which statement about Java's primitive types is true?

Java has no concept of wrapper classes for its primitive types.

Java’s primitive types include strings and arrays.

Java uses classes as object wrappers for primitives.

Java supports 8 primitive types with corresponding wrapper classes. (correct)

What is a key distinction between Java and Kotlin in terms of data types?

Kotlin does not have primitive types and uses classes as wrappers instead. (correct)

Java's boolean type is classified differently than in Kotlin.

Java has a unique type for strings not present in Kotlin.

Kotlin supports both primitive types and wrapper classes.

Which of the following is a correct Kotlin function declaration?

sum(a, b) { return a + b; }

fun sum(a: Int, b: Int): Int { return a + b } (correct)

int sum(int a, int b) { return a + b; }

public sum(int a, int b) { return a + b; }

What is the value range for a Java 'short' type?

-32768 to 32767 Signup and view all the answers

Which statement is true about Kotlin's handling of null values?

Kotlin has built-in null safety features to prevent null references. Signup and view all the answers

What is the significance of the absence of a semi-colon in a Kotlin function definition?

It indicates that Kotlin does not require statement termination. Signup and view all the answers

Which data type in Java has a bit depth of 64 bits?

Double Signup and view all the answers

How does Kotlin represent a character type compared to Java?

Kotlin's character type has a bit depth of 16 bits similar to Java's. Signup and view all the answers

What happens when a secondary constructor is defined in a Kotlin class?

It can invoke the primary constructor using the 'this' keyword. Signup and view all the answers

Which keyword is necessary to allow a Kotlin class to be inherited from?

open Signup and view all the answers

In the given example, how is a trailing comma utilized in Kotlin class declarations?

In property declarations for better formatting. Signup and view all the answers

What does the primary constructor of the Employee class do in relation to the Person class?

It passes a name to the primary constructor of the Person class. Signup and view all the answers

When declaring a class in Kotlin, what must each secondary constructor do?

It must invoke a primary constructor. Signup and view all the answers

What keyword is used to define an initializer block in a Kotlin class?

init Signup and view all the answers

Which statement is true regarding Kotlin primary constructors?

They can only declare read-only properties. Signup and view all the answers

Which of the following creates an instance of the Person class with the age set to null?

val person = Person(“Priscilla”) Signup and view all the answers

In what way does Kotlin simplify class declaration compared to Java?

It requires fewer lines of code. Signup and view all the answers

What is the purpose of the 'init' block in a Kotlin class?

To perform initialization tasks after the primary constructor. Signup and view all the answers

Which constructor syntax is correct for declaring a secondary constructor in Kotlin?

constructor() Signup and view all the answers

What can be said about the age property in the class Person when it is declared as Int? in Kotlin?

It can be a null value. Signup and view all the answers

What is the equivalent Java code for the primary constructor of the Person class?

class Person { final String name; final Integer age; } Signup and view all the answers

What will be the output of the function call `calculate(1, 3)` given the function definition `fun calculate(num1: Int, num2: Int = 2, num3: Int = 4)`?

7 Signup and view all the answers

Which statement correctly describes the return value of the Kotlin function defined as `fun sum(a: Int, b: Int) = a + b`?

It returns the sum of a and b. Signup and view all the answers

What will the value of variable l be if S2 is null?

null Signup and view all the answers

Which function call will allow you to skip the second parameter while still providing the first and third parameters?

calculate(1, num3 = 5) Signup and view all the answers

In Kotlin, which declaration allows re-assignment of values?

var a = 1 Signup and view all the answers

Which of the following statements about safe calls in Kotlin is true?

Safe calls can return a null value if any part of the chain is null. Signup and view all the answers

What is the main advantage of Kotlin's safe calls over traditional null checks in Java?

Safe calls reduce the amount of code needed to handle null cases. Signup and view all the answers

What will happen if you attempt to reassign the value of `val a = 1`?

An error will occur. Signup and view all the answers

What is the output of 'println(b?.length)' if b is assigned null?

null Signup and view all the answers

Which of the following statements about the function `public fun sum(a: Int, b: Int): Int { return a + b }` is correct?

It requires a return type to be defined explicitly. Signup and view all the answers

How is string interpolation represented in Kotlin?

Prepending variables with '$'. Signup and view all the answers

What will the variable `b` hold in the following Kotlin code: `var b: String = 'tim'`?

A mutable string. Signup and view all the answers

In Kotlin, which method form of function declaration is concise yet functional?

public fun sum(a: Int, b: Int): Int = a + b Signup and view all the answers

Which of the following correctly represents the output of 'override fun toString() = “Song{id=$id, title=‘$title’, author=‘$author’}”'?

The method will output the actual values of id, title, and author. Signup and view all the answers

How can you create an array of integers in Kotlin using implicit type declaration?

val num = arrayOf(1, 2, 3, 4) Signup and view all the answers

What will happen if 'tim' or any other property in the chain 'tim?.department?.head?.name' is null?

It will return null. Signup and view all the answers

What do the parameters of the Array constructor in Kotlin represent?

The size of the array and a method that returns the initial value Signup and view all the answers

Which of the following snippets demonstrates a correct use of safe calls in Kotlin?

return user?.address?.zipCode Signup and view all the answers

What will happen if you try to assign null to a non-nullable variable in Kotlin?

A compilation error will occur Signup and view all the answers

How can you safely access the length of a nullable String variable in Kotlin?

Using a null check before accessing length Signup and view all the answers

How do you declare a nullable String variable in Kotlin?

var str: String? = "hku" Signup and view all the answers

Which of the following correctly demonstrates null safety in Kotlin?

If str is non-null, proceed to get str.length Signup and view all the answers

Which snippet would cause a null pointer exception in Kotlin?

var S2: String? = "hku"; val l = S2.length Signup and view all the answers

What is the purpose of the range operator '0..num.size-1' in array traversal in Kotlin?

To define a range of indices for looping through the array Signup and view all the answers

Study Notes