task competed

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

@@ -1,48 +1,144 @@
 package core.basesyntax;
 
+import java.util.NoSuchElementException;
+
 public class ArrayList<T> implements List<T> {
+    private static final int DEFAULT_CAPACITY = 10;
+    private Object[] elements;
+    private int size;
+
+    public ArrayList() {
+        this.elements = new Object[DEFAULT_CAPACITY];
+        this.size = 0;
+    }
+
+    public ArrayList(T[] elements) {
+        if (elements == null) {
+            throw new IllegalArgumentException("Array cannot be null");
+        }
+        this.elements = new Object[DEFAULT_CAPACITY < elements.length
+                ? elements.length : DEFAULT_CAPACITY];
+        int i = 0;
+        for (T elem : elements) {
+            this.elements[i] = elem;
+            i++;
+        }
+        this.size = elements.length;
+    }
+
+    private void grow() {
+        int newCapacity = elements.length + elements.length / 2;
+        Object[] newElements = new Object[newCapacity];
+        System.arraycopy(elements, 0, newElements, 0, size);
+        elements = newElements;
+    }
+
+    private void arrayListIndexOutOfBoundException(int index) {
+        if (index < 0 || index >= size) {
+            throw new ArrayListIndexOutOfBoundsException("Index "
+                    + index + " out of bounds for size " + size);
+        }
+    }
+
     @Override
     public void add(T value) {
-
+        if (this.size >= this.elements.length) {
+            grow();
+        }
+        elements[size] = value;
+        this.size++;
     }
 
     @Override
     public void add(T value, int index) {
-
+        if (index < 0 || index > size) {
+            throw new ArrayListIndexOutOfBoundsException("Index "
+                    + index + " out of bounds for size " + size);
+        }
+        if (this.size >= this.elements.length) {
+            grow();
+        }
+        System.arraycopy(
+                this.elements,
+                index,
+                this.elements,
+                index + 1,
+                size - index
+        );
+        elements[index] = value;
+        size++;
     }
 
     @Override
     public void addAll(List<T> list) {
-
+        if (list == null) {
+            throw new IllegalArgumentException("List cannot be null");
+        }
+        for (int i = 0; i < list.size(); i++) {
+            add(list.get(i));
+        }
     }
 
     @Override
     public T get(int index) {
-        return null;
+        arrayListIndexOutOfBoundException(index);
+        return (T) elements[index];
     }
 
     @Override
     public void set(T value, int index) {
-
+        arrayListIndexOutOfBoundException(index);
+        elements[index] = value;
     }
 
     @Override
     public T remove(int index) {
-        return null;
+        arrayListIndexOutOfBoundException(index);
+        final T removed = (T) this.elements[index];
+        int numMoved = size - index - 1;
+        if (numMoved > 0) {
+            System.arraycopy(
+                    elements,
+                    index + 1,
+                    elements,
+                    index,
+                    numMoved
+            );
+        }
+        elements[size - 1] = null;
+        size--;
+        return removed;
     }
 
     @Override
     public T remove(T element) {
-        return null;
+        int index = -1;
+        for (int i = 0; i <= size - 1; i++) {
+            if (element == null) {
+                if (this.elements[i] == null) {
+                    index = i;
+                    break;
+                }
+            } else {
+                if (element.equals(this.elements[i])) {
+                    index = i;
+                    break;
+                }
+            }
+        }
+        if (index == -1) {
+            throw new NoSuchElementException("Element not found: " + element);
+        }
+        return remove(index);
     }
 
     @Override
     public int size() {
-        return 0;
+        return this.size;
     }
 
     @Override
     public boolean isEmpty() {
-        return false;
+        return size == 0;
     }
 }