Java Reference
In-Depth Information
1. A decimal number with a decimal point in it.
Example s: 1.34 and 3. and 0.23333 .
Due to the way literals are implemented, the value of a double literal may
be only an approximation to the corresponding real value.
2. A number in scientific notation: a decimal number (the period . is option-
al), followed by e or E , followed by a (possibly signed) integer.
Examples : 1.32e20 and 2.1E0 and 1E-5 and 3.14e62 .
The value of a double literal mEi is the value of m with its decimal point
moved i places to the right (if i is positive) or left (if i is negative). For
example, 5.0e-5 is equivalent to .00005.
3. An int literal or a double literal, as in points 1 and 2 above, followed by
d or D . Examples: 1D and 1.2d and 1.3e-30d and 24E20D .
Scientific notation, used in many scientific fields, helps to express numbers
that would otherwise be infeasible to express. For example the googol , a name
coined by Milton Sirotta, a nine-year old, in 1955 is the number consisting of 1
followed by 100 zeroes, 1e100 . Mathematicians would write this as 10 100 . The
width of a human hair is approximately 750,000 angstroms or 7.5e-7 meters.
Each double literal must be in the range of the type. If you type a literal that
is outside its range, your program is syntactically incorrect and will not compile.
Two constants give the largest and smallest positive double values:
Double.MAX_VALUE: 1.7976931348623157E308
Double.MIN_VALUE: 4.9E-324
In addition, three other constants represent other “values” of type double :
1. Double.NaN , meaning “not a number”. Division by 0 produces this value.
2. Double.POSITIVE_INFINITY is produced when the exponent of a posi-
tive number gets too big.
3. Double.NEGATIVE_INFINITY is produced when the exponent of a nega-
tive number gets too big.
The range of the exponent is -324..308 .
Operations of type double
The basic arithmetic operators on type double work as expected:
- : Negation . e.g. -3D evaluates to -3.0 .
+ : Addition . e.g. 420. + 2D evaluates to 422.0 .
- : Subtraction . e.g. 42E1 - .2E1 evaluates to 418.0 .
* : Multiplication . e.g. 42E1 * .2E1 evaluates to 840.0 .
/ : Division . e.g. 1D / 3D evaluates to 0.3333333333333333 .
Division 0D/0D produces the value Double.NaN , meaning “Not a
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