Before you go all functional

Functional1.kt

 val sum = (0 until Integer.MAX_VALUE)
            .map { it.toLong() }
            .sum()
println(sum)

Functional2.kt

val sum = (0 until Integer.MAX_VALUE)
                    .asSequence()
                    .map { it.toLong() }
                    .sum()
println(sum)

Normal1.kt

var sum = 0L
  for (i in 0..Integer.MAX_VALUE - 1) {
    sum += i
  }
println(sum)

Normal2.kt

var sum = 0L
  for (i in 0 until Integer.MAX_VALUE) {
    sum += i
  }
println(sum)

Sum.java

Long sum = 0L;
for (long i = 0; i < Integer.MAX_VALUE; i++) {
			sum += i;
}
System.out.println(sum);