String templates

Building strings is an easy process, but in Java it usually requires long concatenation expressions. Let's jump straight to an example. Here is a string built from multiple elements implemented in Java:

//Java 
String name = "Eva"; 
int age = 27; 
String message = "My name is" + name + "and I am" + age + "years old";

In Kotlin, we can greatly simplify the process of string creation by using string templates. Instead of using concatenation, we can simply place a variable inside a string, using a dollar character to create a placeholder. During interpolation, string placeholders will be replaced with the actual value. Here is an example:

    val name = "Eva" 
    val age = 27 
    val message = "My name is $name and I am $age years old" 
    println(message) 
    //Prints: My name is Eva  and I am 27 years old 

This is as efficient as concatenation, because under the hood the compiled code creates a StringBuilder and put all the parts together. String templates are not limited to single variables. They can also contain whole expressions between the ${, and } characters. It can be a function call that returns the value or property access, as shown in the following snippet:

    val name = "Eva" 
    val message = "My name has ${name.length} characters" 
    println(message) //Prints: My name has 3 characters 

This syntax allows us to create much cleaner code without the need to break the string each time a value from a variable or expression is required to construct strings.