kotlin collection (#2241)

* minor logging fix

* spring security sso

* use basic auth

* use form login

* cleanup

* cleanup

* final cleanup

* second client app for sso

* spring boot bootstrap

* add logic

* cleanup

* add simple controller

* add thymeleaf and security

* minor fix

* minor fix

* add more boot properties

* fix live test

* fix live test

* minor fix

* semaphores

* fix configuration

* kotlin collection

kotlin/src/test/kotlin/com/baeldung/kotlin/CollectionsTest.kt

@@ -0,0 +1,121 @@
+package com.baeldung.kotlin
+
+import org.junit.Test
+import kotlin.test.assertTrue
+import kotlin.test.assertFalse
+import kotlin.test.assertEquals
+
+class CollectionsTest {
+
+    @Test
+    fun whenUseDifferentCollections_thenSuccess () {
+        val theList = listOf("one", "two", "three")
+        assertTrue(theList.contains("two"))     
+
+        val theMutableList = mutableListOf("one", "two", "three")
+        theMutableList.add("four")
+        assertTrue(theMutableList.contains("four"))                        
+
+        val theSet = setOf("one", "two", "three")
+        assertTrue(theSet.contains("three"))    
+
+        val theMutableSet = mutableSetOf("one", "two", "three")
+        theMutableSet.add("four")
+        assertTrue(theMutableSet.contains("four"))                
+
+        val theMap = mapOf(1 to "one", 2 to "two", 3 to "three")
+        assertEquals(theMap[2],"two")  
+
+        val theMutableMap = mutableMapOf(1 to "one", 2 to "two", 3 to "three")
+        theMutableMap[4] = "four"
+        assertEquals(theMutableMap[4],"four")             
+    }
+
+    @Test
+    fun whenSliceCollection_thenSuccess () {
+        val theList = listOf("one", "two", "three")
+        val resultList = theList.slice(1..2)
+
+        assertEquals(2, resultList.size)        
+        assertTrue(resultList.contains("two"))        
+    }
+    
+    @Test
+    fun whenJoinTwoCollections_thenSuccess () {
+        val firstList = listOf("one", "two", "three")
+        val secondList = listOf("four", "five", "six")
+        val resultList = firstList + secondList
+
+        assertEquals(6, resultList.size)   
+        assertTrue(resultList.contains("two"))        
+        assertTrue(resultList.contains("five"))        
+    }      
+    
+    @Test
+    fun whenFilterNullValues_thenSuccess () {
+        val theList = listOf("one", null, "two", null, "three")
+        val resultList = theList.filterNotNull()
+
+        assertEquals(3, resultList.size)        
+    }    
+
+    @Test
+    fun whenFilterNonPositiveValues_thenSuccess () {
+        val theList = listOf(1, 2, -3, -4, 5, -6)
+        val resultList = theList.filter{ it > 0}
+        //val resultList = theList.filter{ x -> x > 0}
+
+        assertEquals(3, resultList.size)  
+        assertTrue(resultList.contains(1))
+        assertFalse(resultList.contains(-4))      
+    }     
+
+    @Test
+    fun whenDropFirstItems_thenRemoved () {
+        val theList = listOf("one", "two", "three", "four")
+        val resultList = theList.drop(2)
+
+        assertEquals(2, resultList.size)        
+        assertFalse(resultList.contains("one"))        
+        assertFalse(resultList.contains("two"))        
+    }  
+
+    @Test
+    fun whenDropFirstItemsBasedOnCondition_thenRemoved () {
+        val theList = listOf("one", "two", "three", "four")
+        val resultList = theList.dropWhile{ it.length < 4 }
+
+        assertEquals(2, resultList.size)        
+        assertFalse(resultList.contains("one"))        
+        assertFalse(resultList.contains("two"))        
+    }      
+
+    @Test
+    fun whenExcludeItems_thenRemoved () {
+        val firstList = listOf("one", "two", "three")
+        val secondList = listOf("one", "three")
+        val resultList = firstList - secondList
+
+        assertEquals(1, resultList.size)        
+        assertTrue(resultList.contains("two"))        
+    }   
+
+    @Test
+    fun whenSearchForExistingItem_thenFound () {
+        val theList = listOf("one", "two", "three")
+
+        assertTrue("two" in theList)        
+    } 
+
+    @Test
+    fun whenGroupItems_thenSuccess () {
+        val theList = listOf(1, 2, 3, 4, 5, 6)
+        val resultMap = theList.groupBy{ it % 3}
+
+        assertEquals(3, resultMap.size)  
+        print(resultMap[1])
+        assertTrue(resultMap[1]!!.contains(1))
+        assertTrue(resultMap[2]!!.contains(5))      
+    } 
+
+}