JDK源码学习：Number

public abstract class Number implements java.io.Serializable {
  public abstract int intValue();

  public abstract long longValue();

  public abstract float floatValue();

  public abstract double doubleValue();

  public byte byteValue() {
    return (byte)intValue();
  }

  public short shortValue() {
    return (short)intValue();
  }
}