Added if-else expression examples in kotlin (#9296)

core-kotlin-modules/core-kotlin-lang-2/src/main/kotlin/com/baeldung/ifelseexpression/IfElseExpressionExample.kt

@@ -0,0 +1,86 @@
+package com.baeldung.ifelseexpression
+
+fun ifStatementUsage(): String {
+    val number = 15
+
+    if (number > 0) {
+        return "Positive number"
+    }
+    return "Positive number not found"
+}
+
+fun ifElseStatementUsage(): String {
+    val number = -50
+
+    if (number > 0) {
+        return "Positive number"
+    } else {
+        return "Negative number"
+    }
+}
+
+fun ifElseExpressionUsage(): String {
+    val number = -50
+
+    val result = if (number > 0) {
+        "Positive number"
+    } else {
+        "Negative number"
+    }
+    return result
+}
+
+fun ifElseExpressionSingleLineUsage(): String {
+    val number = -50
+    val result = if (number > 0) "Positive number" else "Negative number"
+
+    return result
+}
+
+fun ifElseMultipleExpressionUsage(): Int {
+    val x = 24
+    val y = 73
+
+    val result = if (x > y) {
+        println("$x is greater than $y")
+        x
+    } else {
+        println("$x is less than or equal to $y")
+        y
+    }
+    return result
+}
+
+fun ifElseLadderExpressionUsage(): String {
+    val number = 60
+
+    val result = if (number < 0) {
+        "Negative number"
+    } else if (number in 0..9) {
+        "Single digit number"
+    } else if (number in 10..99) {
+        "Double digit number"
+    } else {
+        "Number has more digits"
+    }
+    return result
+}
+
+fun ifElseNestedExpressionUsage(): Int {
+    val x = 37
+    val y = 89
+    val z = 6
+
+    val result = if (x > y) {
+        if (x > z)
+            x
+        else
+            z
+    } else {
+        if (y > z)
+            y
+        else
+            z
+    }
+    return result
+}

core-kotlin-modules/core-kotlin-lang-2/src/test/kotlin/com/baeldung/ifelseexpression/IfElseExpressionExampleTest.kt

@@ -0,0 +1,43 @@
+package com.baeldung.ifelseexpression
+
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertNotEquals
+
+class IfElseExpressionExampleTest {
+
+    @Test
+    fun givenNumber_whenIfStatementCalled_thenReturnsString() {
+        assertEquals("Positive number", ifStatementUsage())
+    }
+
+    @Test
+    fun givenNumber_whenIfElseStatementCalled_thenReturnsString() {
+        assertEquals("Negative number", ifElseStatementUsage())
+    }
+
+    @Test
+    fun givenNumber_whenIfElseExpressionCalled_thenReturnsString() {
+        assertEquals("Negative number", ifElseExpressionUsage())
+    }
+
+    @Test
+    fun givenNumber_whenIfElseExpressionSingleLineCalled_thenReturnsString() {
+        assertEquals("Negative number", ifElseExpressionSingleLineUsage())
+    }
+
+    @Test
+    fun givenNumber_whenIfElseMultipleExpressionCalled_thenReturnsNumber() {
+        assertEquals(73, ifElseMultipleExpressionUsage())
+    }
+
+    @Test
+    fun givenNumber_whenIfElseLadderExpressionCalled_thenReturnsString() {
+        assertEquals("Double digit number", ifElseLadderExpressionUsage())
+    }
+
+    @Test
+    fun givenNumber_whenIfElseNestedExpressionCalled_thenReturnsNumber() {
+        assertEquals(89, ifElseNestedExpressionUsage())
+    }
+}