[KTLN-763] Add samples (#1079)

* [KTLN-763] Add samples

* [KTLN-763] Add samples

Author: LeoColman

core-kotlin-modules/core-kotlin-lang-5/pom.xml

@@ -0,0 +1,16 @@
+<?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-lang-5</artifactId>
+    <name>core-kotlin-lang-5</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>core-kotlin-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+</project>

core-kotlin-modules/core-kotlin-lang-5/src/main/kotlin/com/baeldung/nullable/comparable/ComparableFunctions.kt

@@ -0,0 +1,13 @@
+package com.baeldung.nullable.comparable
+
+fun compareTwoInts(a: Int?, b: Int?): Int? {
+    return a?.compareTo(b ?: return null)
+}
+
+fun Int?.isGreaterThan(other: Int?): Boolean? {
+    return this?.let { it > (other ?: return null) }
+}
+
+fun <T : Comparable<T>> T?.isGreaterThan(other: T?): Boolean? {
+    return this?.let { it > (other ?: return null) }
+}

core-kotlin-modules/core-kotlin-lang-5/src/test/kotlin/com/baeldung/nullable/comparable/NullableComparableUnitTest.kt

@@ -0,0 +1,58 @@
+package com.baeldung.nullable.comparable
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+class NullableComparableUnitTest {
+    @Test
+    fun `compare nullable integers using compareTo`() {
+        val a: Int? = 5
+        val b: Int? = 3
+        val c: Int? = null
+        assertEquals(0, compareTwoInts(a, a))
+        assertEquals(1, compareTwoInts(a, b))
+        assertEquals(-1, compareTwoInts(b, a))
+        assertEquals(null, compareTwoInts(a, c))
+        assertEquals(null, compareTwoInts(c, b))
+    }
+
+    @Test fun `compare nullable integers using extension function`() {
+        val a: Int? = 5
+        val b: Int? = 3
+        val c: Int? = null
+        assertEquals(true, a.isGreaterThan(b))
+        assertEquals(false, b.isGreaterThan(a))
+        assertEquals(null, c.isGreaterThan(a))
+        assertEquals(null, c.isGreaterThan(c))
+    }
+
+    @Test fun `compare generic Int comparable types using extension function`() {
+        val a: Int? = 5
+        val b: Int? = 3
+        val c: Int? = null
+        assertEquals(true, a.isGreaterThan(b))
+        assertEquals(false, b.isGreaterThan(a))
+        assertEquals(false, b.isGreaterThan(b))
+        assertEquals(null, c.isGreaterThan(b))
+    }
+
+    @Test fun `compare generic String comparable types using extension function`() {
+        val a: String? = "ABC"
+        val b: String? = "ZXY"
+        val c: String? = null
+        assertEquals(true, b.isGreaterThan(a))
+        assertEquals(false, a.isGreaterThan(b))
+        assertEquals(false, b.isGreaterThan(b))
+        assertEquals(null, c.isGreaterThan(b))
+    }
+
+    @Test fun `compare nullable integers using compareValues function`() {
+        val a: Int? = 5
+        val b: Int? = 3
+        val c: Int? = null
+        assertEquals(1, compareValues(a, b))
+        assertEquals(-1, compareValues(b, a))
+        assertEquals(1, compareValues(a, c))
+        assertEquals(-1, compareValues(c, a))
+        assertEquals(0, compareValues(c, c)) }
+}

core-kotlin-modules/pom.xml

@@ -55,6 +55,7 @@
         <module>core-kotlin-lang-2</module>
         <module>core-kotlin-lang-3</module>
         <module>core-kotlin-lang-4</module>
+        <module>core-kotlin-lang-5</module>
         <module>core-kotlin-lang-scope</module>
         <module>core-kotlin-lang-oop</module>
         <module>core-kotlin-lang-oop-2</module>