JAVA

java double to long

long num = Double.valueOf(d).longValue()

java long to double

Long l = new Long(15552451L);
double d = l.doubleValue();

long to double in java

//It'll work upto three decimal places when converted from long to double
//Here, 'time' is a variable converted from long to double
double dble = Double.valueOf(String.format(Locale.ENGLISH, "%1$.3f",  time/3600.000));