我有以下两种型号的观察员: class MyObserver < ActiveRecord::Observer
observe :my_first_model, :my_second_model
def after_create(record)
x = if record.instance_of?(MyFirstModel)
# x is set to
我正在尝试使Android手机计算Pi的n个小数。为此,我正在使用此代码: public class Pi {
private static final BigDecimal TWO = new BigDecimal(2);
private static final BigDecimal FOUR = new BigDecimal(4);
private String nummer;