Kotlin Basics of Kotlin Basic examples
Example
1.The Unit return type declaration is optional for functions. The following codes are equivalent.
fun printHello(name: String?): Unit {
if (name != null)
println("Hello ${name}")
}
fun printHello(name: String?) {
...
}
2.Single-Expression functions:When a function returns a single expression, the curly braces can be omitted and the body is specified after = symbol
fun double(x: Int): Int = x * 2
Explicitly declaring the return type is optional when this can be inferred by the compiler
fun double(x: Int) = x * 2
3.String interpolation: Using string values is easy.
In java:
int num=10
String s = "i =" + i;
In Kotlin
val num = 10
val s = "i = $num"
4.In Kotlin, the type system distinguishes between references that can hold null (nullable references) and those that can not (non-null references). For example, a regular variable of type String can not hold null:
var a: String = "abc"
a = null // compilation error
To allow nulls, we can declare a variable as nullable string, written String?:
var b: String? = "abc"
b = null // ok
5.In Kotlin,== actually checks for equality of values.By convention, an expression like a == b is translated to
a?.equals(b) ?: (b === null)
