passed checkstyle and tests

src/main/java/core/basesyntax/ArrayList.java

@@ -1,48 +1,121 @@
 package core.basesyntax;
 
+import java.util.NoSuchElementException;
+
 public class ArrayList<T> implements List<T> {
-    @Override
-    public void add(T value) {
+    private static final Object[] EMPTY_ELEMENTDATA = {};
+    private static final int DEFAULT_CAPACITY = 10;
+    private Object[] elementData;
+    private int size;
 
+    public ArrayList() {
+        this.elementData = EMPTY_ELEMENTDATA;
+        this.size = 0;
     }
 
-    @Override
-    public void add(T value, int index) {
+    private void checkIndex(int index) {
+        if (index < 0 || index >= size) {
+            throw new ArrayListIndexOutOfBoundsException("Index " + index
+                    + " is out of bounds for size " + size);
+        }
+    }
+
+    private void checkIndexForAdd(int index) {
+        if (index < 0 || index > size) {
+            throw new ArrayListIndexOutOfBoundsException("Index " + index
+                    + " is out of bounds for size " + size);
+        }
+    }
+
+    private void ensureCapacity() {
+        ensureCapacity(size + 1);
+    }
 
+    private void ensureCapacity(int minCapacity) {
+        if (minCapacity > elementData.length) {
+            int newLength = elementData.length == 0 ? DEFAULT_CAPACITY
+                    : (int) (elementData.length * 1.5);
+            if (newLength < minCapacity) {
+                newLength = minCapacity;
+            }
+            Object[] newElementData = new Object[newLength];
+            System.arraycopy(elementData,0, newElementData, 0, size);
+            this.elementData = newElementData;
+        }
     }
 
     @Override
-    public void addAll(List<T> list) {
+    public void add(T value) {
+        ensureCapacity();
+        this.elementData[size] = value;
+        size++;
+    }
 
+    @Override
+    public void add(T value, int index) {
+        checkIndexForAdd(index);
+        ensureCapacity();
+        System.arraycopy(elementData, index, elementData, index + 1, size - index);
+        elementData[index] = value;
+        size++;
     }
 
     @Override
-    public T get(int index) {
-        return null;
+    public void addAll(List<T> list) {
+        ensureCapacity(size + list.size());
+        for (int i = 0; i < list.size(); i++) {
+            elementData[size] = list.get(i);
+            size++;
+        }
     }
 
     @Override
     public void set(T value, int index) {
+        checkIndex(index);
+        elementData[index] = value;
+    }
 
+    @Override
+    public T get(int index) {
+        checkIndex(index);
+        return (T) elementData[index];
     }
 
     @Override
     public T remove(int index) {
-        return null;
+        checkIndex(index);
+        int numMoved = size - index - 1;
+        T removedValue = (T) elementData[index];
+        System.arraycopy(elementData, index + 1, elementData, index, numMoved);
+        elementData[--size] = null;
+        return removedValue;
     }
 
     @Override
     public T remove(T element) {
-        return null;
+        if (element == null) {
+            for (int i = 0; i < size; i++) {
+                if (elementData[i] == null) {
+                    return remove(i);
+                }
+            }
+        } else {
+            for (int i = 0; i < size; i++) {
+                if (element.equals(elementData[i])) {
+                    return remove(i);
+                }
+            }
+        }
+        throw new NoSuchElementException("Element " + element + " not found in the list");
     }
 
     @Override
     public int size() {
-        return 0;
+        return size;
     }
 
     @Override
     public boolean isEmpty() {
-        return false;
+        return size == 0;
     }
 }