Add an element to the ArrayList

ArrayList.java

public class ArrayList<E> {
  transient Object[] elementData;
  private static final int DEFAULT_CAPACITY = 10; // (4)
  private static final Object[] EMPTY_ELEMENTDATA = {};
  private int size;
  
  public boolean add(E e) {
    ensureCapacityInternal(size + 1); // (1)
    elementData[size++] = e; // (6)
    return true;
  }
  
  public void ensureCapacity(int minCapacity) {
    int minExpand = (elementData != EMPTY_ELEMENTDATA) ? 0 : DEFAULT_CAPACITY;

    if (minCapacity > minExpand) {
      ensureExplicitCapacity(minCapacity);
    }
  }

  private void ensureCapacityInternal(int minCapacity) {
    if (elementData == EMPTY_ELEMENTDATA) { // (2)
      minCapacity = Math.max(DEFAULT_CAPACITY, minCapacity);
    }

    ensureExplicitCapacity(minCapacity);
  }

  private void ensureExplicitCapacity(int minCapacity) {
    modCount++;

    if (minCapacity - elementData.length > 0)
      grow(minCapacity); // (3)
  }
    
  private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;

  private void grow(int minCapacity) {
    // overflow-conscious code
    int oldCapacity = elementData.length;
    int newCapacity = oldCapacity + (oldCapacity >> 1);
    if (newCapacity - minCapacity < 0)
      newCapacity = minCapacity;
    if (newCapacity - MAX_ARRAY_SIZE > 0)
      newCapacity = hugeCapacity(minCapacity);
    // minCapacity is usually close to size, so this is a win:
    elementData = Arrays.copyOf(elementData, newCapacity); // (5)
  }

  private static int hugeCapacity(int minCapacity) {
    if (minCapacity < 0) // overflow
      throw new OutOfMemoryError();
    return (minCapacity > MAX_ARRAY_SIZE) ?
      Integer.MAX_VALUE :
      MAX_ARRAY_SIZE;
  }

  public int size() {
    return size;
  }
}