This code performs integer multiply and then converts the result to a long, as in:

 
	long convertDaysToMilliseconds(int days) { return 1000*3600*24*days; } 
If the multiplication is done using long arithmetic, you can avoid the possibility that the result will overflow. For example, you could fix the above code to:
 
	long convertDaysToMilliseconds(int days) { return 1000L*3600*24*days; } 
or
 
	static final long MILLISECONDS_PER_DAY = 24L*3600*1000;
	long convertDaysToMilliseconds(int days) { return days * MILLISECONDS_PER_DAY; }