jwalgemoed

@ExperimentalContracts
fun main(args: Array<String>) {
    var assign: String
    val time = measureTimeMillis {
        assign = "Value Assigned"
    }
    println("$time ms. spent assigning: '$assign'")
}

@ExperimentalContracts

jwalgemoed

fun main(args: Array<String>) {
    var assign: String
    val time = measureTimeMillis {
        assign = "Value Assigned"
    }
    println("$time ms. spent assigning: '$assign!!'")
}

private inline fun measureTimeMillis(block: () -> Unit): Long {
    val start = System.currentTimeMillis()

jwalgemoed

contract { 
  returns(true) implies (this@isComplete != null) 
}

jwalgemoed

@ExperimentalContracts
fun User?.isComplete(): Boolean {
    contract { returns(true) implies (this@isComplete != null) }
    return this != null && this.isValid()
}

jwalgemoed

fun printUserDetails(user: User?) {
    if(user.isComplete()) {
        println("${user!!.name} ${user!!.email}")
    }
}

jwalgemoed

fun printUserDetails(user: User?) {
    if(user?.isValid()) {
        println("${user.name} ${user.email}")
    }
}

jwalgemoed

data class User(val name: String?, val email: String?) {
    fun isValid() = !name.isNullOrBlank() && name.length > 3 
                    && !email.isNullOrBlank() && email.length > 3
}

jwalgemoed

var variable = returnValue(); // Type is inferred from the return type of the method

// Method declaration
public String returnValue() {
  return "w00p";
}

jwalgemoed

var strings = Arrays.asList("a", "b", "c");
for(var str: strings) {
  System.out.println(str);
}

jwalgemoed

// We can explicitly work against interfaces
List<String> list = new ArrayList(); // type: List<String>

// Using var, we can't do this without casting
var list = new ArrayList<String>();  // Inferred type ArrayList<String>
var list = (List)new ArrayList<String>(); // Inferred type List<String>