常用的API

scanner nextint()

Random nextint(X)

Math ceil() floor() round() abs()

arrays tostring() sort()

System  currentTimeMillis() coyarrsy

date gettime() settime()

　　simpledateformate format() parse()

calendar get(calendar.year) set(calendar.year,2014) getTime() getInstance(****,****)  add(calendar.year,1)

string  indexof() concat() equals() length() charAt() substring() split() reaplace() toCharArray() getBytes()

stringbuilder