akexorcist

// Not Null
val user : User = ...
user.apply {
    ...
}

// Nullable
val user : User? = ...
user?.apply {
    ...

akexorcist

val user : User? = null
val result = user?.let {
    ...
}
// result = null

akexorcist

val user : User? = null
val result = user?.apply {
    ...
}?.also {
    ...
}?.run {
    ...
}

akexorcist

fun startHere() {
  doAnything {
    System.out.println("Do something before 2nd thing")
  }
}

fun doAnything(block: () -> Unit) {
  System.out.println("Do 1st thing")
  block()
  System.out.println("Do 2nd thing")

akexorcist

fun startHere() {
  var addResult = calculate(10, 3, { x, y ->
    x + y
  })

  var subtractResult = calculate(10, 3, { x, y ->
    x - y
  })
  ...
}

akexorcist

fun doSomething() {
  ...
  doComplexTask("Akexorcist", { name ->
    "Mr.${name.trim()}"
  }, { fullName ->
    System.out.println("Hello, $fullName")
  })
}
fun doComplexTask(name: String,
                method1: (name: String) -> String,

akexorcist

fun startHere() {
  var addResult = calculate(10, 3, { x, y ->
    x + y
  })
  ...
}
fun calculate(x: Int, 
              y: Int, 
              equation: (x: Int, y: Int) -> Int): Int {
  // Do something

akexorcist

public final void startHere() {
  int addResult = this.calculate(10, 3, (Function2)null.INSTANCE);
  ...
}
public final int calculate(int x, int y, @NotNull Function2 equation) {
  Intrinsics.checkParameterIsNotNull(equation, "equation"); 
  // Do something
  return ((Number)equation.invoke(x, y)).intValue();
}

akexorcist

for (index in 1..100) {
  var addResult = calculate(10, index, { x, y ->
    x + y
  })
  ...
}

akexorcist

fun startHere() {
  for (index in 0..100) {
    var addResult = calculate(10, index, { x, y ->
      x + y
    })
    ...
  }
}
inline fun calculate(x: Int, 
                     y: Int,