[int-bin-str] create numbers module; int-> binary string (#790)

Author: sk1418

core-kotlin-modules/core-kotlin-numbers/README.md

@@ -0,0 +1,5 @@
+## Core Kotlin Strings
+
+This module contains articles about core Kotlin numbers.
+
+### Relevant Articles

core-kotlin-modules/core-kotlin-numbers/pom.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-kotlin-numbers</artifactId>
+    <name>core-kotlin-numbers</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>core-kotlin-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+    </dependencies>
+
+</project>

core-kotlin-modules/core-kotlin-numbers/src/test/kotlin/com/baeldung/intToBinaryRepresentation/IntToBinaryRepresentationUnitTest.kt

@@ -0,0 +1,35 @@
+package com.baeldung.intToBinaryRepresentation
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+fun Int.to32BitBinaryString(): String =
+    toUInt().toString(2).padStart(Int.SIZE_BITS, '0')
+
+class IntToBinaryRepresentationUnitTest {
+    @Test
+    fun `when using Integer's toBinaryString() then get expected result`() {
+        assertEquals("10110", Integer.toBinaryString(22))
+        assertEquals("101010", Integer.toBinaryString(42))
+        assertEquals("11111111111111111111111111111110", Integer.toBinaryString(-2))
+    }
+
+    @Test
+    fun `when using kotlin's toString(2) then get expected result`() {
+        assertEquals("10110", 22.toString(radix = 2))
+        assertEquals("101010", 42.toString(2)) // we can omit the parameter name "radix"
+
+        assertEquals("-10", (-2).toString(2))
+        assertEquals("11111111111111111111111111111110", (-2).toUInt().toString(2))
+
+        assertEquals("10110", 22.toUInt().toString(radix = 2))
+        assertEquals("101010", 42.toUInt().toString(2))
+    }
+
+    @Test
+    fun `when using to32BitBinaryString then get expected result`() {
+        assertEquals("00000000000000000000000000010110", 22.to32BitBinaryString())
+        assertEquals("00000000000000000000000000101010", 42.to32BitBinaryString())
+        assertEquals("11111111111111111111111111111110", (-2).to32BitBinaryString())
+    }
+}

core-kotlin-modules/pom.xml

@@ -54,6 +54,7 @@
         <module>core-kotlin-lang-oop</module>
         <module>core-kotlin-lang-oop-2</module>
         <module>core-kotlin-lang-oop-3</module>
+        <module>core-kotlin-numbers</module>
         <module>core-kotlin-strings</module>
         <module>core-kotlin-strings-2</module>
         <module>core-kotlin-strings-3</module>