final int x = 1;
// x = 2;  // cannot assign value to final variable 'x'
final A y = new A();
y.a = 1;

public native int hashCode()

public boolean equals(Object obj)

protected native Object clone() throws CloneNotSupportedException

public String toString()

public final native Class<?> getClass()

protected void finalize() throws Throwable {}

public final native void notify()

public final native void notifyAll()

public final native void wait(long timeout) throws InterruptedException

public final void wait(long timeout, int nanos) throws InterruptedException

public final void wait() throws InterruptedException

/**
  * 默认初始容量大小
  */
 private static final int DEFAULT_CAPACITY = 10;
 

 private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {};

 /**
  *默认构造函数，使用初始容量10构造一个空列表(无参数构造)
  */
 public ArrayList() {
     this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA;
 }
 
 /**
  * 带初始容量参数的构造函数。（用户自己指定容量）
  */
 public ArrayList(int initialCapacity) {
     if (initialCapacity > 0) {//初始容量大于0
         //创建initialCapacity大小的数组
         this.elementData = new Object[initialCapacity];
     } else if (initialCapacity == 0) {//初始容量等于0
         //创建空数组
         this.elementData = EMPTY_ELEMENTDATA;
     } else {//初始容量小于0，抛出异常
         throw new IllegalArgumentException("Illegal Capacity: "+
                                            initialCapacity);
     }
 }


/**
 *构造包含指定collection元素的列表，这些元素利用该集合的迭代器按顺序返回
 *如果指定的集合为null，throws NullPointerException。 
 */
  public ArrayList(Collection<? extends E> c) {
     elementData = c.toArray();
     if ((size = elementData.length) != 0) {
         // c.toArray might (incorrectly) not return Object[] (see 6260652)
         if (elementData.getClass() != Object[].class)
             elementData = Arrays.copyOf(elementData, size, Object[].class);
     } else {
         // replace with empty array.
         this.elementData = EMPTY_ELEMENTDATA;
     }
 }