diff --git a/src/main/java/core/basesyntax/ArrayList.java b/src/main/java/core/basesyntax/ArrayList.java
index 4bf0c8598..9920b6a8e 100644
--- a/src/main/java/core/basesyntax/ArrayList.java
+++ b/src/main/java/core/basesyntax/ArrayList.java
@@ -4,40 +4,27 @@
 import java.util.NoSuchElementException;
 
 public class ArrayList<T> implements List<T> {
+    private static final int DEFAULT_CAPACITY = 10;
     private T[] elements;
     private int size;
-    private static final int DEFAULT_CAPACITY = 10;
-    private static final int START_SIZE = 0;
 
     public ArrayList() {
         elements = (T[]) new Object[DEFAULT_CAPACITY];
-        size = START_SIZE;
+        size = 0;
     }
 
     @Override
     public void add(T value) {
-        if (size == elements.length) {
-            int newCapacity = (int) (elements.length * 1.5);
-            elements = Arrays.copyOf(elements, newCapacity);
-        }
+        growIfNeeded();
         elements[size] = value;
         size++;
     }
 
     @Override
     public void add(T value, int index) {
-        if (index < 0 || index > size) {
-            throw new ArrayListIndexOutOfBoundsException("Invalid index: " + index);
-        }
-
-        if (size == elements.length) {
-            int newCapacity = (int) (elements.length * 1.5);
-            elements = Arrays.copyOf(elements, newCapacity);
-        }
-
-        for (int i = size; i > index; i--) {
-            elements[i] = elements[i - 1];
-        }
+        checkIndexForAdd(index);
+        growIfNeeded();
+        shiftRight(index);
         elements[index] = value;
         size++;
     }
@@ -47,50 +34,38 @@ public void addAll(List<T> list) {
         if (list == null) {
             throw new NullPointerException("The provided list is null");
         }
-
+        ensureCapacity(size + list.size());
         for (int i = 0; i < list.size(); i++) {
-            this.add(list.get(i));
+            add(list.get(i));
         }
     }
 
     @Override
     public T get(int index) {
-        if (index < 0 || index >= size) {
-            throw new ArrayListIndexOutOfBoundsException("Invalid index: " + index);
-        }
+        checkIndex(index);
         return elements[index];
     }
 
     @Override
     public void set(T value, int index) {
-        if (index < 0 || index >= size) {
-            throw new ArrayListIndexOutOfBoundsException("Invalid index: " + index);
-        }
+        checkIndex(index);
         elements[index] = value;
     }
 
     @Override
     public T remove(int index) {
-        if (index < 0 || index >= size) {
-            throw new ArrayListIndexOutOfBoundsException("Invalid index: " + index);
-        }
-
+        checkIndex(index);
         T removedElement = elements[index];
-
-        for (int i = index; i < size - 1; i++) {
-            elements[i] = elements[i + 1];
-        }
-
-        elements[size - 1] = null;
+        shiftLeft(index);
         size--;
-
         return removedElement;
     }
 
     @Override
     public T remove(T element) {
         for (int i = 0; i < size; i++) {
-            if (elements[i].equals(element)) {
+            if ((elements[i] == null && element == null) || (elements[i]
+                    != null && elements[i].equals(element))) {
                 return remove(i);
             }
         }
@@ -106,4 +81,48 @@ public int size() {
     public boolean isEmpty() {
         return size == 0;
     }
+
+    private void growIfNeeded() {
+        if (size == elements.length) {
+            int newCapacity = (int) (elements.length * 1.5);
+            elements = Arrays.copyOf(elements, newCapacity);
+        }
+    }
+
+    private void ensureCapacity(int minCapacity) {
+        if (minCapacity > elements.length) {
+            int newCapacity = elements.length;
+            while (newCapacity < minCapacity) {
+                newCapacity = (int) (newCapacity * 1.5);
+            }
+            elements = Arrays.copyOf(elements, newCapacity);
+        }
+    }
+
+    private void shiftRight(int index) {
+        for (int i = size; i > index; i--) {
+            elements[i] = elements[i - 1];
+        }
+    }
+
+    private void shiftLeft(int index) {
+        for (int i = index; i < size - 1; i++) {
+            elements[i] = elements[i + 1];
+        }
+        elements[size - 1] = null;
+    }
+
+    private void checkIndex(int index) {
+        if (index < 0 || index >= size) {
+            throw new ArrayListIndexOutOfBoundsException("Index " + index
+                    + " is out of bounds. Size: " + size);
+        }
+    }
+
+    private void checkIndexForAdd(int index) {
+        if (index < 0 || index > size) {
+            throw new ArrayListIndexOutOfBoundsException("Index " + index
+                    + " is out of bounds for add. Size: " + size);
+        }
+    }
 }