Java with BlueJ, 2016a

26 CHAPTER 2. BASICS
2.3.2 Numeric Data Types: float, double
These data types are used to represent values that have decimal places. For
example, the numbers 11.5, 12.25, -300.123, and0.0 are written with
decimal places. Even the value zero written as 0.0 is a double.
The float and double types differ with respect to the number of significant
digits they store (approximately 7 for float and 16 for double) and the overall
magnitude of a value that can be represented. The table below shows the
amount of memory used and the maximum value per type:
data type memory maximum
float 4bytes 3.4028235 × 10 38
double 8bytes 1.7976931348623157 × 10 308
Of course a programmer can perform calculations on doubles andfloats.
The operators we will discuss at this time include +, -, *, and / as shown
in the following table.
operator example of use example’s result
+ 7.1 + 1.1 8.2
- 12.1 - 5.0 7.1
* 2.2 * 2.2 4.84
/ 10 / 4 2.5
Listing 2.4 illustrates some simple double calculations in order to compute
and display fuel consumption as litres per 100 kilometres travelled.
Listing 2.4: Perform simple double calculations
1 public class FuelConsumption
2 {
3 public static void main(String[] args)
4 {
5 // Calculate fuel consumption as
6 // litres per 100 kilometres travelled.
7 // All calculations involve doubles.
8 double litres , km, km100;
9 litres = 60.6;
10 km = 500.25;
11 km100 = km/100.0;
12 // calculate litres per 100km
13 double consumption = litres/km100;