From 4948895c58d71cee2a15724f745afbf470ea58a4 Mon Sep 17 00:00:00 2001
From: ArtShevchenko89 <a.sheva2004@gmail.com>
Date: Fri, 15 May 2026 16:44:48 +0200
Subject: [PATCH 1/2] Implement ArrayList with core methods: add, addAll, get,
 set, remove, size, and isEmpty. Add helper methods checkIndex and
 growIfArrayFull

---
 src/main/java/core/basesyntax/ArrayList.java | 96 ++++++++++++++++++--
 1 file changed, 88 insertions(+), 8 deletions(-)

diff --git a/src/main/java/core/basesyntax/ArrayList.java b/src/main/java/core/basesyntax/ArrayList.java
index 8d6477943..40cad4bc8 100644
--- a/src/main/java/core/basesyntax/ArrayList.java
+++ b/src/main/java/core/basesyntax/ArrayList.java
@@ -1,48 +1,128 @@
 package core.basesyntax;
 
+import java.util.NoSuchElementException;
+import java.util.Objects;
+
 public class ArrayList<T> implements List<T> {
+    private static final int DEFAULT_CAPACITY = 10;
+    private static final double GROWTH_FACTOR = 1.5;
+
+    private T[] data;
+    private int size;
+
+    public ArrayList() {
+        this.data = (T[]) new Object[DEFAULT_CAPACITY];
+        this.size = 0;
+    }
+
+    public ArrayList(T[] elementData, int size) {
+        if (elementData == null) {
+            throw new IllegalArgumentException("elementData is null");
+        }
+        if (size < 0 || size > elementData.length) {
+            throw new IllegalArgumentException("Invalid size: " + size);
+        }
+        this.data = elementData;
+        this.size = size;
+    }
+
     @Override
     public void add(T value) {
-
+        if (size == data.length) {
+            growIfArrayFull();
+        }
+        data[size] = value;
+        size++;
     }
 
     @Override
     public void add(T value, int index) {
+        if (index < 0 || index > size) {
+            throw new ArrayListIndexOutOfBoundsException(
+                    "Index " + index + " is out of bounds for size " + size);
+        }
 
+        if (size == data.length) {
+            growIfArrayFull();
+        }
+
+        System.arraycopy(data, index, data, index + 1, size - index);
+        data[index] = value;
+        size++;
     }
 
     @Override
     public void addAll(List<T> list) {
-
+        if (list == null) {
+            throw new IllegalArgumentException("list is null");
+        }
+        for (int i = 0; i < list.size(); i++) {
+            add(list.get(i));
+        }
     }
 
     @Override
     public T get(int index) {
-        return null;
+        checkIndex(index);
+        return data[index];
     }
 
     @Override
     public void set(T value, int index) {
-
+        checkIndex(index);
+        data[index] = value;
     }
 
     @Override
     public T remove(int index) {
-        return null;
+        checkIndex(index);
+
+        final T removed = data[index];
+
+        int elementsToMove = size - index - 1;
+        if (elementsToMove > 0) {
+            System.arraycopy(data, index + 1, data, index, elementsToMove);
+        }
+
+        data[size - 1] = null;
+        size--;
+
+        return removed;
     }
 
     @Override
     public T remove(T element) {
-        return null;
+        for (int i = 0; i < size; i++) {
+            if (Objects.equals(data[i], element)) {
+                T removed = data[i];
+                remove(i);
+                return removed;
+            }
+        }
+        throw new NoSuchElementException("element not found");
     }
 
     @Override
     public int size() {
-        return 0;
+        return size;
     }
 
     @Override
     public boolean isEmpty() {
-        return false;
+        return size == 0;
+    }
+
+    private void checkIndex(int index) {
+        if (index < 0 || index >= size) {
+            throw new ArrayListIndexOutOfBoundsException(
+                    "Index " + index + " is out of bounds for size " + size);
+        }
+    }
+
+    private void growIfArrayFull() {
+        int newCapacity = (int) (data.length * GROWTH_FACTOR);
+        T[] newData = (T[]) new Object[newCapacity];
+        System.arraycopy(data, 0, newData, 0, size);
+        data = newData;
     }
 }

From 8808349946ae3a4735f6e9fc30515bbbb0dea04c Mon Sep 17 00:00:00 2001
From: ArtShevchenko89 <a.sheva2004@gmail.com>
Date: Fri, 15 May 2026 17:32:30 +0200
Subject: [PATCH 2/2] Fix ArrayList implementation: remove Objects usage and
 improve null-safe comparison

---
 src/main/java/core/basesyntax/ArrayList.java | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/main/java/core/basesyntax/ArrayList.java b/src/main/java/core/basesyntax/ArrayList.java
index 40cad4bc8..62086b32e 100644
--- a/src/main/java/core/basesyntax/ArrayList.java
+++ b/src/main/java/core/basesyntax/ArrayList.java
@@ -1,7 +1,6 @@
 package core.basesyntax;
 
 import java.util.NoSuchElementException;
-import java.util.Objects;
 
 public class ArrayList<T> implements List<T> {
     private static final int DEFAULT_CAPACITY = 10;
@@ -93,7 +92,8 @@ public T remove(int index) {
     @Override
     public T remove(T element) {
         for (int i = 0; i < size; i++) {
-            if (Objects.equals(data[i], element)) {
+            if ((data[i] == null && element == null)
+                    || (data[i] != null && data[i].equals(element))) {
                 T removed = data[i];
                 remove(i);
                 return removed;