list

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

@@ -1,48 +1,104 @@
 package core.basesyntax;
 
+import java.util.NoSuchElementException;
+
 public class ArrayList<T> implements List<T> {
+    private static final int DEFAULT_CAPACITY = 10;
+    private Object[] elementData;
+    private int size;
+
+    public ArrayList() {
+        elementData = new Object[DEFAULT_CAPACITY];
+    }
+
+    private void ensureCapacity() {
+        if (size >= elementData.length) {
+            int newCapacity = elementData.length + (elementData.length >> 1);
+            Object[] newArray = new Object[newCapacity];
+            System.arraycopy(elementData, 0, newArray, 0, elementData.length);
+            elementData = newArray;
+        }
+    }
+
+    private void checkIndex(int index) {
+        if (index < 0 || index >= size) {
+            throw new ArrayListIndexOutOfBoundsException("Index: " + index + ", Size: " + size);
+        }
+    }
+
+    private void checkIndexForAdd(int index) {
+        if (index < 0 || index > size) {
+            throw new ArrayListIndexOutOfBoundsException("Index: " + index + ", Size: " + size);
+        }
+    }
+
     @Override
     public void add(T value) {
-
+        ensureCapacity();
+        elementData[size++] = value;
     }
 
     @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 void addAll(List<T> list) {
-
+        for (int i = 0; i < list.size(); i++) {
+            add(list.get(i));
+        }
     }
 
+    @SuppressWarnings("unchecked")
     @Override
     public T get(int index) {
-        return null;
+        checkIndex(index);
+        return (T) elementData[index];
     }
 
     @Override
     public void set(T value, int index) {
-
+        checkIndex(index);
+        elementData[index] = value;
     }
 
+    @SuppressWarnings("unchecked")
     @Override
     public T remove(int index) {
-        return null;
+        checkIndex(index);
+        T removedElement = (T) elementData[index];
+        int numMoved = size - index - 1;
+        if (numMoved > 0) {
+            System.arraycopy(elementData, index + 1, elementData, index, numMoved);
+        }
+        elementData[--size] = null; // Clear the last element
+        return removedElement;
     }
 
     @Override
     public T remove(T element) {
-        return null;
+        for (int i = 0; i < size; i++) {
+            if (elementData[i] == null ? element == null : elementData[i].equals(element)) {
+                T removed = (T) elementData[i];
+                remove(i);
+                return removed;
+            }
+        }
+        throw new NoSuchElementException("Element not found: " + element);
     }
 
     @Override
     public int size() {
-        return 0;
+        return size;
     }
 
     @Override
     public boolean isEmpty() {
-        return false;
+        return size == 0;
     }
 }