Money calculations

jeorg-kotlin-crums/jeorg-kotlin-crums-4-variance/src/main/kotlin/org/jesperancinha/ktd/FloatVsDouble.kt

@@ -0,0 +1,48 @@
+package org.jesperancinha.ktd
+
+class FloatVsDouble {
+    companion object {
+        @JvmStatic
+        fun main(args: Array<String>) {
+            val floatNumber = 7.3333333333333333333333333333333f
+            println(floatNumber)
+            println("The number $floatNumber has ${floatNumber.toString().length - 1} digits in precision")
+            val doubleNumber = 7.3333333333333333333333333333333
+            println(doubleNumber)
+            println("The number $doubleNumber has ${doubleNumber.toString().length - 1} digits in precision")
+            val bigDecimal = "7.3333333333333333333333333333333".toBigDecimal()
+            println("The number $bigDecimal has ${bigDecimal.toString().length - 1} digits in precision")
+
+            val value1 = 9
+            val value2 = 9
+
+            println("This is the result of a bad idea sum ${badIdeaSum(value1, value2)}")
+            println("This is the result of a good idea sum ${goodIdeaSum(value1, value2)}")
+        }
+
+        /**
+         * This function will try to sum
+         * value1,000,000,000,000,000,000
+         * with
+         * value2,000,000,000,000,000,000
+         * correctly
+         */
+        private fun goodIdeaSum(value1: Int, value2: Int): String {
+            return ((value1 + value2).toBigDecimal().multiply(1_000_000_000_000_000_000.toBigDecimal() )).toString()
+        }
+
+        /**
+         * This function will try to sum
+         * value1,000,000,000,000,000,000
+         * with
+         * value2,000,000,000,000,000,000
+         * using a terrible idea
+         * NOTE that this idea is defended by some interviewers in selection processes.
+         * Do not feel bad about it if the interviewer rejects your application because of this.
+         * You probably wouldn't want to work in a place with these criteria any way.
+         */
+        private fun badIdeaSum(value1: Int, value2: Int): String {
+           return ((value1 + value2) * 1_000_000_000_000_000_000).toString()
+        }
+    }
+}