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