seconds = days * 24 * 60 * 60; // convert to seconds
distance = lightspeed * seconds; // compute distance
System.out.print("In " + days);
System.out.print(" days light will travel about ");
System.out.println(distance + " miles.");
}
}
This program generates the following output:
In 1000 days light will travel about 16070400000000 miles.
Clearly, the result could not have been held in an int variable.
Floating-Point Types
Floating-point numbers, also known as real numbers, are used when evaluating expressions
that require fractional precision. For example, calculations such as square root, or transcendentals
such as sine and cosine, result in a value whose precision requires a floating-point type. Java
implements the standard (IEEE754) set of floating-point types and operators. There are two
kinds of floating-point types, float and double, which represent single- and double-precision
numbers, respectively. Their width and ranges are shown here:
Name
Width in Bits
Approximate Range
64
4.9e324 to 1.8e+308
double
32
1.4e045 to 3.4e+038
float
Each of these floating-point types is examined next.
float
The type float specifies a single-precision value that uses 32 bits of storage. Single precision is
faster on some processors and takes half as much space as double precision, but will become
imprecise when the values are either very large or very small. Variables of type float are useful
when you need a fractional component, but don't require a large degree of precision. For
example, float can be useful when representing dollars and cents.
Here are some example float variable declarations:
float hightemp, lowtemp;
double
Double precision, as denoted by the double keyword, uses 64 bits to store a value. Double
precision is actually faster than single precision on some modern processors that have been
optimized for high-speed mathematical calculations. All transcendental math functions, such
as sin( ), cos( ), and sqrt( ), return double values. When you need to maintain accuracy over
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