Updated March 2, 2023
Introduction to Kotlin Use
Kotlin use function is used to execute the block function of the resource basically kotlin is the general purpose programming language, and JetBrains develop it. Kotlin builds IDE Intellij IDEA. There are multiple situations where we can use the resource; after using the resource, we need to take care of this lifecycle so it will not leak any resources. Suppose we are reading any file, then we need to close it after the user; suppose we are not closing this file it will go into an unstable state. By using the use of keywords, we are achieving this feature.
What is Kotlin Use?
Kotlin is used to run the JVM also; it will run side by side with java. The first kotlin will start as a language with the development of android; then, it will quickly spread with a community of java because the feature of kotlin is very useful while developing applications. Use is the predefined and reserved keywords that we are using in the kotlin language of programming. It will contain the special meaning of compiler. We cannot use keywords of use as identifiers in our program code. Use keyword is the part of the syntax, so we cannot use the same as an identifier.
Kotlin Use Function
The function of kotlin use is the inline function which was used to execute the given function block by using the resources. The use function in kotlin correctly closes the resources once after we complete our operation. The function contains the added benefit if suppose there is an exception while executing the function block. We can expect that the resource will close down correctly.
Below is the syntax of the use function in kotlin as follows. We are also using the inline function with the use function in kotlin.
Syntax:
inline fun (function of inline) <T : Closeable? (closable object), R> T.use (kotlin use function) (block: (T) x (use function block) -> R) : R (source)In the above syntax, inline will define as a function that we are using with the use function in a kotlin. The parameter fun is used for returning the result of the function block. We are returning the result in the use function by using a fun parameter. Closable is the function block that was used to process the block of function. It is the resource used in the function. We are using the use keyword, which was used in the inline function.
Block keyword in a use function used to process the function of the resource, which was closeable. We are also using the source keyword with the function of use in kotlin. It will execute the given block of function onto the resource, which closes down correctly whether we have thrown an exception.
Below example shows how we are using the use function in kotlin as follows:
Code:
import java.io.File
fun main (args: Array<String>) {
val inputfile = inputfile ("kotlinfile.txt")
inputfile.bufferedReader ().use {
println (inputfile.readText ())
}
}Output:
In the above example, we are using the name fun as the main. Also, we are using the argument as array string. We are using the input file name as kotlinfile.txt for providing the input to the buffered Reader function. We are using the use function to open files for reading purposes.
Kotlin Use Keyword
In the use keyword of kotlin, we need to follow the rules and the naming convention. The name identifier starts with the underscore or letter followed by zero and digits. At the time of using the use keyword in it, whitespace is not accepted. The use keyword identifier does not contain any symbols; also, the identifier of the use keyword is not case sensitive. At the time of creating variables by using use keyword, we need to choose the appropriate name. The keyword is divided into two types i.e. soft keywords and hard keywords. Use keywords are predefined, and reserved words are used in a language of kotlin; it will contain the special meaning of the compiler.
To learn the use keyword, we need to define the java function. When using the keyword in it first, we need to execute the function call as input with the lambda expression and store the result temporarily. The second function is returning the result. The use keyword is helpful in two places at the time reading the file and accessing a property of another object.
The below example shows how we can use the use keyword.
Code:
import java.io.File
fun main(args: Array<String>) {
FileInputStream ("inputfile.txt") . use {
input ->
var usekeyword = input.read ()
}
}Output:
In the above example, we are using the name fun as the main. We are using the input file name as inputfile.txt for providing the input to the file input stream function. We are using the use function with input.read function.
Examples of Kotlin Use
To understand the use keyword, we need to check the feature of prior java 7, managing the java resources and the same is closed after using is very difficult for example, check the below example in below example we can see that we need to close the file after reading.
Code:
private static void printFile() throws IOException {
InputStream ip = null;
try {
ip = new FileInputStream ("ip.txt");
} finally {
If (ip != null) {
ip.close ();
} }Output:
In the below example, we can see that exception is thrown inside from the try block when we are using the input object. It is also thrown into the final block because we are trying to close an object of input. Now we are calling the final block when the try block is throwing an exception. Suppose both the try and finally block will give the exceptions then we need to use the following code.
Code:
private static void printFile() throws IOException {
InputStream ip = null;
try (FileInputStream ip = new FileInputStream ("input. txt")) {
int data-input.read();
} finally {
If (ip != null){
ip.close ();
} }Output:
In the above example, try block will finish the execution the object of the file input stream closes automatically.
Code:
fun main(args: Array<String>) {
FileInputStream ("file.txt") . use {
ip ->
var usekeyword = ip.read ()
}
}Output:
Conclusion
Use is the predefined and reserved keywords that we are using in the kotlin language of programming. The function is used to execute the block function of the resource. Basically, it is the general-purpose programming language, and JetBrains develop it.
Recommended Articles
This is a guide to Kotlin Use. Here we discuss the introduction, kotlin use function, and keywords and examples, respectively. You may also have a look at the following articles to learn more –
