java.math
public enum class: RoundingMode [javadoc |
source]
java.lang.Enum
java.math.RoundingMode
Specifies a
rounding behavior for numerical operations
capable of discarding precision. Each rounding mode indicates how
the least significant returned digit of a rounded result is to be
calculated. If fewer digits are returned than the digits needed to
represent the exact numerical result, the discarded digits will be
referred to as the
discarded fraction regardless the digits'
contribution to the value of the number. In other words,
considered as a numerical value, the discarded fraction could have
an absolute value greater than one.
Each rounding mode description includes a table listing how
different two-digit decimal values would round to a one digit
decimal value under the rounding mode in question. The result
column in the tables could be gotten by creating a
{@code BigDecimal} number with the specified value, forming a
MathContext object with the proper settings
({@code precision} set to {@code 1}, and the
{@code roundingMode} set to the rounding mode in question), and
calling round on this number with the
proper {@code MathContext}. A summary table showing the results
of these rounding operations for all rounding modes appears below.
Summary of Rounding Operations Under Different Rounding Modes
| Result of rounding input to one digit with the given
rounding mode |
|---|
| Input Number | {@code UP} |
{@code DOWN} |
{@code CEILING} |
{@code FLOOR} |
{@code HALF_UP} |
{@code HALF_DOWN} |
{@code HALF_EVEN} |
{@code UNNECESSARY} |
| 5.5 | 6 | 5 | 6 | 5 | 6 | 5 | 6 | throw {@code ArithmeticException} |
| 2.5 | 3 | 2 | 3 | 2 | 3 | 2 | 2 | throw {@code ArithmeticException} |
| 1.6 | 2 | 1 | 2 | 1 | 2 | 2 | 2 | throw {@code ArithmeticException} |
| 1.1 | 2 | 1 | 2 | 1 | 1 | 1 | 1 | throw {@code ArithmeticException} |
| 1.0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| -1.0 | -1 | -1 | -1 | -1 | -1 | -1 | -1 | -1 |
| -1.1 | -2 | -1 | -1 | -2 | -1 | -1 | -1 | throw {@code ArithmeticException} |
| -1.6 | -2 | -1 | -1 | -2 | -2 | -2 | -2 | throw {@code ArithmeticException} |
| -2.5 | -3 | -2 | -2 | -3 | -3 | -2 | -2 | throw {@code ArithmeticException} |
| -5.5 | -6 | -5 | -5 | -6 | -6 | -5 | -6 | throw {@code ArithmeticException} |
This {@code enum} is intended to replace the integer-based
enumeration of rounding mode constants in BigDecimal
(BigDecimal#ROUND_UP , BigDecimal#ROUND_DOWN ,
etc. ).
Also see:
- BigDecimal
- MathContext
- author:
Josh - Bloch
- author:
Mike - Cowlishaw
- author:
Joseph - D. Darcy
- since:
1.5 -
| Field Summary |
|---|
| final int | oldMode | Rounding mode to assert that the requested operation has an exact
result, hence no rounding is necessary. If this rounding mode is
specified on an operation that yields an inexact result, an
{@code ArithmeticException} is thrown.
Example:
| Input Number |
Input rounded to one digit
with {@code UNNECESSARY} rounding
|
|---|
| 5.5 | throw {@code ArithmeticException} |
| 2.5 | throw {@code ArithmeticException} |
| 1.6 | throw {@code ArithmeticException} |
| 1.1 | throw {@code ArithmeticException} |
| 1.0 | 1 |
| -1.0 | -1 |
| -1.1 | throw {@code ArithmeticException} |
| -1.6 | throw {@code ArithmeticException} |
| -2.5 | throw {@code ArithmeticException} |
| -5.5 | throw {@code ArithmeticException} |
|
| Method from java.math.RoundingMode Summary: |
|---|
|
valueOf |
| Method from java.math.RoundingMode Detail: |
|---|
 public static RoundingMode valueOf(int rm) {
switch(rm) {
case BigDecimal.ROUND_UP:
return UP;
case BigDecimal.ROUND_DOWN:
return DOWN;
case BigDecimal.ROUND_CEILING:
return CEILING;
case BigDecimal.ROUND_FLOOR:
return FLOOR;
case BigDecimal.ROUND_HALF_UP:
return HALF_UP;
case BigDecimal.ROUND_HALF_DOWN:
return HALF_DOWN;
case BigDecimal.ROUND_HALF_EVEN:
return HALF_EVEN;
case BigDecimal.ROUND_UNNECESSARY:
return UNNECESSARY;
default:
throw new IllegalArgumentException("argument out of range");
}
}
Returns the {@code RoundingMode} object corresponding to a
legacy integer rounding mode constant in BigDecimal . |
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