done

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

@@ -1,48 +1,122 @@
 package core.basesyntax;
+import java.util.Arrays;
+import java.util.NoSuchElementException;
 
 public class ArrayList<T> implements List<T> {
+    private Object[] arrayList;
+    private int size;
+    private final int defaultSize = 10;
+
+    public ArrayList() {
+        arrayList = new Object[defaultSize];
+        size = 0;
+    }
+
+    public void ensureCapacity() {
+        if (size == arrayList.length) {
+            arrayList = Arrays.copyOf(arrayList, arrayList.length + (arrayList.length >> 1));
+        }
+    }
+
+    public void ensureCapacity(int requiredCapacity) {
+        if (requiredCapacity > arrayList.length) {
+            int newCapacity = Math.max((int) (arrayList.length * 1.5), requiredCapacity);
+            arrayList = Arrays.copyOf(arrayList, newCapacity);
+        }
+    }
+
+    public void ensureIndexForAdd(int index) {
+        if (index < 0 || index > size) {
+            throw new ArrayListIndexOutOfBoundsException("Index " + index + " out of bounds");
+        }
+    }
+
+    public void ensureIndex(int index) {
+        if (index < 0 || index >= size) {
+            throw new ArrayListIndexOutOfBoundsException("Index " + index + " out of bounds");
+        }
+    }
     @Override
     public void add(T value) {
-
+        ensureCapacity();
+        arrayList[size] = value;
+        size++;
     }
 
     @Override
     public void add(T value, int index) {
-
+        ensureIndexForAdd(index);
+        ensureCapacity();
+        for (int i = size - 1; i >= index; i--) {
+            arrayList[i + 1] = arrayList[i];
+        }
+        arrayList[index] = value;
+        size++;
     }
 
     @Override
     public void addAll(List<T> list) {
-
+        ensureCapacity(size + list.size());
+        for (int i = 0; i < list.size(); i++) {
+            arrayList[size + i] = list.get(i);
+        }
+        size += list.size();
     }
 
     @Override
     public T get(int index) {
-        return null;
+        ensureIndex(index);
+        return (T) arrayList[index];
     }
 
     @Override
     public void set(T value, int index) {
-
+        ensureIndex(index);
+        arrayList[index] = value;
     }
 
     @Override
     public T remove(int index) {
-        return null;
+        ensureIndex(index);
+        final T removedElement = (T) arrayList[index];
+        for (int i = index; i < size - 1; i++) {
+            arrayList[i] = arrayList[i + 1];
+        }
+        arrayList[size - 1] = null;
+        size--;
+        return removedElement;
     }
 
     @Override
     public T remove(T element) {
-        return null;
+        boolean isExist = false;
+        int indexOfElement = 0;
+        for (int i = 0; i < arrayList.length; i++) {
+            if (arrayList[i] == null ? element == null : arrayList[i].equals(element)) {
+                isExist = true;
+                indexOfElement = i;
+                break;
+            }
+        }
+        if (!isExist) {
+            throw new NoSuchElementException("There is no such element");
+        }
+        final T removedElement = (T) arrayList[indexOfElement];
+        for (int i = indexOfElement; i < size - 1; i++) {
+            arrayList[i] = arrayList[i + 1];
+        }
+        arrayList[size - 1] = null;
+        size--;
+        return removedElement;
     }
 
     @Override
     public int size() {
-        return 0;
+        return size;
     }
 
     @Override
     public boolean isEmpty() {
-        return false;
+        return size == 0;
     }
 }