KTLN-641: Convert Octal Number to Decimal and Vice-Versa (#592)

Co-authored-by: Tapan Avasthi <[email protected]>

Author: tapankavasthi

kotlin-math/src/main/kotlin/com/baeldung/math/octalconversion/OctalConversion.kt

@@ -0,0 +1,52 @@
+package com.baeldung.math.octalconversion
+
+import java.math.BigInteger
+
+fun octalToDecimalUsingParseInt(octal: String): Int {
+    return Integer.parseInt(octal, 8)
+}
+
+fun octalToDecimalUsingIteration(octal: String): Int {
+    var decimal = 0
+    var power = 0
+    for (i in octal.length - 1 downTo 0) {
+        val digit = octal[i].toString().toInt()
+        decimal += digit * Math.pow(8.0, power.toDouble()).toInt()
+        power++
+    }
+    return decimal
+}
+
+fun String.octalToDecimal(): Int {
+    return Integer.parseInt(this, 8)
+}
+
+fun octalToDecimalUsingToInt(octal: String): Int {
+    return octal.toInt(8)
+}
+
+fun octalToDecimalUsingBigInteger(octal: String): BigInteger {
+    return BigInteger(octal, 8)
+}
+
+fun decimalToOctalUsingIntegerToString(decimal: Int): String {
+    return Integer.toString(decimal, 8)
+}
+
+fun decimalToOctalUsingStringInterpolation(decimal: Int): String {
+    return "%o".format(decimal)
+}
+
+fun Int.decimalToOctal(): String {
+    return Integer.toString(this, 8)
+}
+
+fun decimalToOctalUsingIteration(decimal: Int): String {
+    var octal = ""
+    var num = decimal
+    while (num > 0) {
+        octal = (num % 8).toString() + octal
+        num /= 8
+    }
+    return octal
+}

kotlin-math/src/test/kotlin/octalconversion/OctalDecimalConverstionUnitTest.kt

@@ -0,0 +1,53 @@
+package com.baeldung.math.octalconversion
+
+import org.junit.jupiter.api.Assertions
+import org.junit.jupiter.api.Test
+import java.math.BigInteger
+
+class OctalDecimalConverstionUnitTest {
+
+    @Test
+    fun `test octal to decimal conversion using octalToDecimalUsingParseInt should give correct result`() {
+        Assertions.assertEquals(28, octalToDecimalUsingParseInt("34"))
+    }
+
+    @Test
+    fun `test octal to decimal conversion using octalToDecimalUsingIteration should give correct result`() {
+        Assertions.assertEquals(28, octalToDecimalUsingIteration("34"))
+    }
+
+    @Test
+    fun `test octal to decimal conversion using octalToDecimal extension function should give correct result`() {
+        Assertions.assertEquals(28, "34".octalToDecimal())
+    }
+
+    @Test
+    fun `test octal to decimal conversion using octalToDecimalUsingToInt should give correct result`() {
+        Assertions.assertEquals(28, octalToDecimalUsingToInt("34"))
+    }
+
+    @Test
+    fun `test octal to decimal conversion using octalToDecimalUsingBigInteger should give correct result`() {
+        Assertions.assertEquals(BigInteger.valueOf(28), octalToDecimalUsingBigInteger("34"))
+    }
+
+    @Test
+    fun `test decimal to octal conversion using decimalToOctalUsingIntegerToString should give correct result`() {
+        Assertions.assertEquals("34", decimalToOctalUsingIntegerToString(28))
+    }
+
+    @Test
+    fun `test decimal to octal conversion using decimalToOctalUsingStringInterpolation should give correct result`() {
+        Assertions.assertEquals("34", decimalToOctalUsingStringInterpolation(28))
+    }
+
+    @Test
+    fun `test decimal to octal conversion using decimalToOctal extension function should give correct result`() {
+        Assertions.assertEquals("34", 28.decimalToOctal())
+    }
+
+    @Test
+    fun `test decimal to octal conversion using decimalToOctalUsingIteration should give correct result`() {
+        Assertions.assertEquals("34", decimalToOctalUsingIteration(28))
+    }
+}