code_for_KTLN-748 (#929)

Author: vinaywadhwa

core-kotlin-modules/core-kotlin-concurrency-3/src/test/java/com/baeldung/concurrentmodificationexception/ConcurrentModificationExceptionUnitTest.kt

@@ -0,0 +1,76 @@
+package com.baeldung.concurrentmodificationexception
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import java.util.*
+import java.util.concurrent.CopyOnWriteArrayList
+
+class ConcurrentModificationExceptionUnitTest {
+
+
+    @Test
+    fun `given list when remove during iteration then throw ConcurrentModificationException`() {
+        val numbers = mutableListOf(1, 2, 3, 4, 5)
+
+        assertThrows<ConcurrentModificationException> {
+            for (item in numbers) {
+                if (item == 3) {
+                    numbers.remove(item)
+                }
+            }
+        }
+    }
+
+    @Test
+    fun `given list when remove with iterator then list is updated`() {
+        val numbers = mutableListOf(1, 2, 3, 4, 5)
+        val iterator = numbers.iterator()
+        while (iterator.hasNext()) {
+            val number = iterator.next()
+            if (number == 3) {
+                iterator.remove()
+            }
+        }
+
+        assertEquals(listOf(1, 2, 4, 5), numbers)
+    }
+
+    @Test
+    fun `given list when removeAll by condition then list is updated`() {
+        val numbers = mutableListOf(1, 2, 3, 4, 5)
+        numbers.removeAll { number -> number == 3 }
+
+        assertEquals(listOf(1, 2, 4, 5), numbers)
+    }
+
+    @Test
+    fun `given list and copy when modify copy then update list`() {
+        var numbers = mutableListOf(1, 2, 3, 4, 5)
+        val copyNumbers = numbers.toMutableList()
+
+        for (number in numbers) {
+            if (number == 3) {
+                copyNumbers.remove(number)
+            }
+        }
+
+        numbers = copyNumbers
+
+        assertEquals(listOf(1, 2, 4, 5), numbers)
+    }
+
+    @Test
+    fun `given CopyOnWriteArrayList when remove items then items removed`() {
+        val list = CopyOnWriteArrayList(listOf(1, 2, 3, 4, 5))
+
+        for (item in list) {
+            if (item == 3) {
+                list.remove(item)
+            }
+        }
+
+        assertEquals(listOf(1, 2, 4, 5), list)
+    }
+
+}