Add ArrayList

src/main/java/de/szut/App.java

@@ -0,0 +1,13 @@
+package de.szut;
+
+/**
+ * Hello world!
+ *
+ */
+public class App 
+{
+    public static void main( String[] args )
+    {
+        System.out.println( "Hello World!" );
+    }
+}

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

@@ -0,0 +1,55 @@
+package de.szut;
+
+import java.util.Arrays;
+
+public class MyArrayList {
+
+    private static final int INITIAL_CAPACITY = 10;
+
+    private int[] array;
+    private int size;
+
+    public MyArrayList() {
+        this.array = new int[INITIAL_CAPACITY];
+        this.size = 0;
+    }
+
+    public int size() {
+        return size;
+    }
+
+    public boolean add(int value) {
+        ensureCapacity();
+        array[size++] = value;
+        return true;
+    }
+
+    public void remove(int index) {
+        if (index < 0 || index >= size) {
+            throw new RuntimeException("Dieser Index existiert nicht!");
+        }
+
+        for (int i = index; i < size - 1; i++) {
+            array[i] = array[i + 1];
+        }
+
+        array[--size] = 0;
+    }
+
+
+    public boolean contains(int value) {
+        for (int i = 0; i < size; i++) {
+            if (array[i] == value) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private void ensureCapacity() {
+        if (size == array.length) {
+            int newCapacity = array.length + INITIAL_CAPACITY;
+            array = Arrays.copyOf(array, newCapacity);
+        }
+    }
+}

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

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+package de.szut;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.fail;
+
+public class MyArrayListTest {
+
+    private MyArrayList list;
+
+    @Before
+    public void setUp() {
+        list = new MyArrayList();
+    }
+
+
+
+    @Test
+    public void add_ShouldReturnTrueAndIncreaseSize() {
+        assertThat(list.size(), is(0));
+
+        boolean added1 = list.add(5);
+        assertThat(added1, is(true));
+        assertThat(list.size(), is(1));
+        assertThat(list.contains(5), is(true));
+
+        boolean added2 = list.add(10);
+        assertThat(added2, is(true));
+        assertThat(list.size(), is(2));
+        assertThat(list.contains(10), is(true));
+    }
+
+    @Test
+    public void remove_ShouldRemoveElementAndDecreaseSize() {
+        list.add(5);
+        list.add(10);
+        list.add(15);
+
+        assertThat(list.size(), is(3));
+
+        list.remove(1);
+
+        assertThat(list.size(), is(2));
+        assertThat(list.contains(5), is(true));
+        assertThat(list.contains(10), is(false));
+        assertThat(list.contains(15), is(true));
+    }
+
+    @Test
+    public void remove_ShouldThrowExceptionForInvalidIndex() {
+        list.add(5);
+
+        assertThat(list.size(), is(1));
+
+        try {
+            list.remove(1);
+            fail("Expected RuntimeException was not thrown");
+        } catch (RuntimeException e) {
+            assertThat(e.getMessage(), is("Dieser Index existiert nicht!"));
+            assertThat(list.size(), is(1));
+        }
+    }
+
+    @Test
+    public void size_ShouldReturnZeroInitially() {
+        assertThat(list.size(), is(0));
+    }
+
+    @Test
+    public void size_ShouldBeZeroInitially() {
+
+        assertThat(list.size(), is(0));
+    }
+
+    @Test
+    public void size_ShouldIncreaseWhenElementAdded() {
+        list.add(5);
+
+        assertThat(list.size(), is(1));
+    }
+
+    @Test
+    public void size_ShouldIncreaseProperlyWhenMultipleElementsAdded() {
+        list.add(5);
+        list.add(10);
+
+        assertThat(list.size(), is(2));
+    }
+
+    @Test
+    public void size_ShouldDecreaseWhenElementRemoved() {
+        list.add(5);
+        list.add(10);
+
+        list.remove(0);
+
+        assertThat(list.size(), is(1));
+    }
+
+    @Test
+    public void size_ShouldNotDecreaseBelowZero() {
+        list.add(5);
+
+        list.remove(0);
+
+        assertThat(list.size(), is(0));
+    }
+
+
+    @Test
+    public void contains_ShouldReturnTrueIfElementPresent() {
+        list.add(5);
+        list.add(10);
+        list.add(15);
+
+        assertThat(list.contains(10), is(true));
+    }
+
+    @Test
+    public void contains_ShouldReturnFalseIfElementNotPresent() {
+        list.add(5);
+        list.add(10);
+        list.add(15);
+
+        assertThat(list.contains(20), is(false));
+    }
+
+    @Test
+    public void dynamicSize_ShouldIncreaseAsElementsAdded() {
+        for (int i = 1; i <= 15; i++) {
+            boolean added = list.add(i);
+            assertThat(added, is(true));
+        }
+
+        assertThat(list.size(), is(15));
+
+        for (int i = 1; i <= 15; i++) {
+            assertThat(list.contains(i), is(true));
+        }
+    }
+}