Kotlin interview questions finishing
1. What is kotlin
Kotlin is a statically typed programming language developed by JetBrains and runs on the JVM .
2. Why use Kotlin language
Kotlin language is concise and efficient, there is not so much redundant code, and it is empty safe.
3. Explain the extension function
The extension function is used to extend the class without deriving from the class
4. What does null safety in Kotlin mean?
The feature of null safety is to avoid the problem of null pointer exceptions, and can also be used to distinguish between null references and non-null references.
5. Why is Kotlin and Java interoperable?
Because they are the same after compilation for jvm, byte code runs on jvm after compilation
6. Is there a ternary operator in kotlin
does not exist
7. How to declare a variable in Kotlin
var name: String
8. How many constructors are there in Kotlin
Two, one is the primary constructor, the other is the secondary constructor
9. Talk about the extension method of Java.io.file in Kotlin
bufferedReader，readBytes，readText，forEachLine，readLines
10. How does kotlin handle empty exceptions
Use elvis operator to handle null exceptions? :,? .
11. What are the characteristics? Kotlin has but java does not
null safety，operator overloading，coroutines， range expressions， smart cast， compaion object
12. The role of data classes in kotlin
The data class contains basic data types, but it does not contain any functional functions
13. Can java code be converted into kotlin code?
Can be converted in AndroidStudio or JetBrains
14. Does Kotlin allow macros?
Kotlin does not support macros
15. The default behavior of the Kotlin class
Kotlin is final by default. Because kotlin supports multiple class inheritance, the cost of open classes is much higher than final classes
16. Does kotlin support primitive data types?
Kotlin does not support primitive data types
17. What is the range operator
The range operator is used to traverse a range, represented by two dots
for（i in 1..5）
print（i）
18. Does Kotlin provide additional functions for standard Java libraries and classes?
The kotlin program runs on a standard java virtual machine, so there is no difference between kotlin and java at this level, and java can also be run directly in the kotlin program
19. Define a volatile variable in Kotlin
volatile var x: Long? = null
20.What is the role of abstraction in kotlin
Abstraction is the most important concept of object-oriented programming. The characteristics of abstract classes: You know what functions this class has, but you don't know how to implement these functions and which functions are implemented in detail.
21. How to compare two strings in Kotlin
（1）==
（2）.equals(Any?)
22. What is the use of the following code?
bar {
System.out.println("1111")
}
As a function, bar is receiving an expression as a parameter. This expression prints a line of string
23, Kotlin higher-order functions