Abgabe: Mika

src/main/java/de/szut/mylists/MyArrayList.java

@@ -1,5 +1,59 @@
 package de.szut.mylists;
 
-public class MyArrayList {
+import java.util.Arrays;
 
+public class MyArrayList {
+    private Integer[] internalArray = new Integer[10];
+    private int size;
+
+    public void add(int value) {
+        if(size == internalArray.length)
+            resize();
+
+        internalArray[size++] = value;
+    }
+
+    public int get(int index) {
+        if(index < 0 || index >= size)
+            throw new RuntimeException("Dieser Index existiert nicht!");
+
+        return internalArray[index];
+    }
+
+    public void remove(int index) {
+        Integer[] newArray;
+
+        if(index < 0 || index >= size)
+            throw new RuntimeException("Dieser Index existiert nicht!");
+
+        newArray = new Integer[internalArray.length];
+
+        int newIndexCounter = 0;
+        for(int i = 0; i < size; i++) {
+            if(i == index)
+                continue;
+
+            newArray[newIndexCounter++] = internalArray[i];
+        }
+
+        internalArray = newArray;
+        size = newIndexCounter;
+    }
+
+    public boolean contains(int value) {
+        if(size == 0)
+            return false;
+
+        return Arrays.stream(internalArray).anyMatch(e -> e != null && e.equals(value));
+    }
+
+    public int size() {
+        return size;
+    }
+
+    private void resize() {
+        Integer[] newArray = new Integer[internalArray.length + 10];
+        System.arraycopy(internalArray, 0, newArray, 0, size);
+        internalArray = newArray;
+    }
 }

src/test/java/de/szut/mylists/MyArrayListTest.java

@@ -1,5 +1,125 @@
 package de.szut.mylists;
 
-public class MyArrayListTest {
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
 
+import java.util.List;
+import java.util.stream.Stream;
+
+import static org.assertj.core.api.Assertions.*;
+
+public class MyArrayListTest {
+    MyArrayList list;
+
+    @BeforeEach
+    public void setUp() {
+        list = new MyArrayList();
+    }
+
+    @ParameterizedTest
+    @MethodSource("generateData")
+    public void testIfAddDoesNotThrowsException(List<Integer> data) {
+        assertThatNoException().isThrownBy(() -> data.forEach(list::add));
+    }
+
+    @ParameterizedTest
+    @MethodSource("generateData")
+    public void testThatRemoveThrowsExceptionWhenNegativeIndex(List<Integer> data) {
+        data.forEach(list::add);
+
+        assertThatThrownBy(() -> list.remove(-1))
+                .isExactlyInstanceOf(RuntimeException.class)
+                .hasMessage("Dieser Index existiert nicht!");
+    }
+
+    @ParameterizedTest
+    @MethodSource("generateData")
+    public void testThatGetThrowsExceptionWhenNegativeIndex(List<Integer> data) {
+        data.forEach(list::add);
+
+        assertThatThrownBy(() -> list.get(-1))
+                .isExactlyInstanceOf(RuntimeException.class)
+                .hasMessage("Dieser Index existiert nicht!");
+    }
+
+    @ParameterizedTest
+    @MethodSource("generateData")
+    public void testThatRemoveActuallyRemovesElement(List<Integer> data) {
+        data.forEach(list::add);
+
+        list.remove(0);
+        assertThat(list.get(0)).isNotEqualTo(data.get(0));
+    }
+
+    @ParameterizedTest
+    @MethodSource("generateData")
+    public void testThatRemoveDecreasesSize(List<Integer> data) {
+        data.forEach(list::add);
+
+        list.remove(0);
+        assertThat(list.size()).isEqualTo(data.size() - 1);
+    }
+
+    @ParameterizedTest
+    @MethodSource("generateData")
+    public void testIfRemovingRearrangeArray(List<Integer> data) {
+        data.forEach(list::add);
+
+        list.remove(0);
+        assertThat(list.get(0)).isEqualTo(data.get(1));
+    }
+
+    @Test
+    public void testIfRemovingInvalidIndexIsThrowing_RuntimeException() {
+        list.add(1);
+
+        assertThatThrownBy(() -> list.remove(1))
+                .isExactlyInstanceOf(RuntimeException.class)
+                .hasMessage("Dieser Index existiert nicht!");
+    }
+
+    @Test
+    public void testIfRemovingValidIndexIsNotThrowing_RuntimeException() {
+        list.add(1);
+        assertThatNoException().isThrownBy(() -> list.remove(0));
+    }
+
+    @ParameterizedTest
+    @MethodSource("generateData")
+    public void testIfSizeGivesCorrectNumberOfElements(List<Integer> data) {
+        data.forEach(list::add);
+
+        assertThat(list.size()).isEqualTo(data.size());
+    }
+
+    @ParameterizedTest
+    @MethodSource("generateData")
+    public void testIfContainsReturnsTrueIfItFindsTheElement(List<Integer> data) {
+        data.forEach(list::add);
+
+        data.forEach(e -> assertThat(list.contains(e)).isTrue());
+    }
+
+    @Test
+    public void testIfContainsReturnsFalseIfItDoesNotFindTheElement() {
+        list.add(1);
+
+        assertThat(list.contains(2)).isFalse();
+    }
+
+    @Test
+    public void testIfContainsOnEmptyListDoesNotThrowError() {
+        assertThatNoException().isThrownBy(() -> list.contains(2));
+    }
+
+    private static Stream<Arguments> generateData() {
+        return Stream.of(
+                Arguments.of(List.of(1, 2, 3)),
+                Arguments.of(List.of(8, 2)),
+                Arguments.of(List.of(-1, -98, Integer.MIN_VALUE, Integer.MAX_VALUE))
+        );
+    }
 }