Class ArrayList

classpath/java/util/ArrayList.java:17–209

import java.io.ObjectOutputStream;

public class ArrayList<T> extends AbstractList<T> implements java.io.Serializable, RandomAccess {
  private static final int MinimumCapacity = 16;

  private Object[] array;
  private int size;

  public ArrayList(int capacity) {
    resize(capacity);
  }

  public ArrayList() {
    this(0);
  }

  public ArrayList(Collection<? extends T> source) {
    this(source.size());
    addAll(source);
  }

  private void grow(int newSize) {
    if (array == null || newSize > array.length) {
      resize(Math.max(newSize, array == null
                      ? MinimumCapacity : array.length * 2));
    }
  }

  private void shrink(int newSize) {
    if (array.length / 2 >= MinimumCapacity && newSize <= array.length / 3) {
      resize(array.length / 2);
    }
  }

  private void resize(int capacity) {
    Object[] newArray = null;
    if (capacity != 0) {
      if (array != null && array.length == capacity) {
        return;
      }

      newArray = new Object[capacity];
      if (array != null) {
        System.arraycopy(array, 0, newArray, 0, size);
      }
    }
    array = newArray;
  }

  private static boolean equal(Object a, Object b) {
    return (a == null && b == null) || (a != null && a.equals(b));
  }

  public int size() {
    return size;
  }

  public void ensureCapacity(int capacity) {
    grow(capacity);
  }