public enum RoundingMode extends Enum<RoundingMode>
Each rounding mode description includes a table listing how
different twodigit 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
BigDecimal
number with the specified value, forming a
MathContext
object with the proper settings
(precision
set to 1
, and the
roundingMode
set to the rounding mode in question), and
calling round
on this number with the
proper MathContext
. A summary table showing the results
of these rounding operations for all rounding modes appears below.
Result of rounding input to one digit with the given rounding mode  

Input Number  UP 
DOWN 
CEILING 
FLOOR 
HALF_UP 
HALF_DOWN 
HALF_EVEN 
UNNECESSARY 
5.5  6  5  6  5  6  5  6  throw ArithmeticException 
2.5  3  2  3  2  3  2  2  throw ArithmeticException 
1.6  2  1  2  1  2  2  2  throw ArithmeticException 
1.1  2  1  2  1  1  1  1  throw 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 ArithmeticException 
1.6  2  1  1  2  2  2  2  throw ArithmeticException 
2.5  3  2  2  3  3  2  2  throw ArithmeticException 
5.5  6  5  5  6  6  5  6  throw ArithmeticException 
This enum
is intended to replace the integerbased
enumeration of rounding mode constants in BigDecimal
(BigDecimal.ROUND_UP
, BigDecimal.ROUND_DOWN
,
etc. ).
BigDecimal
,
MathContext
Enum Constant and Description 

CEILING
Rounding mode to round towards positive infinity.

DOWN
Rounding mode to round towards zero.

FLOOR
Rounding mode to round towards negative infinity.

HALF_DOWN
Rounding mode to round towards "nearest neighbor"
unless both neighbors are equidistant, in which case round
down.

HALF_EVEN
Rounding mode to round towards the "nearest neighbor"
unless both neighbors are equidistant, in which case, round
towards the even neighbor.

HALF_UP
Rounding mode to round towards "nearest neighbor"
unless both neighbors are equidistant, in which case round up.

UNNECESSARY
Rounding mode to assert that the requested operation has an exact
result, hence no rounding is necessary.

UP
Rounding mode to round away from zero.

Modifier and Type  Method and Description 

static RoundingMode 
valueOf(int rm)
Returns the
RoundingMode object corresponding to a
legacy integer rounding mode constant in BigDecimal . 
static RoundingMode 
valueOf(String name)
Returns the enum constant of this type with the specified name.

static RoundingMode[] 
values()
Returns an array containing the constants of this enum type, in
the order they are declared.

public static final RoundingMode UP
Example:
Input Number  Input rounded to one digit with UP rounding


5.5  6 
2.5  3 
1.6  2 
1.1  2 
1.0  1 
1.0  1 
1.1  2 
1.6  2 
2.5  3 
5.5  6 
public static final RoundingMode DOWN
Example:
Input Number  Input rounded to one digit with DOWN rounding


5.5  5 
2.5  2 
1.6  1 
1.1  1 
1.0  1 
1.0  1 
1.1  1 
1.6  1 
2.5  2 
5.5  5 
public static final RoundingMode CEILING
RoundingMode.UP
;
if negative, behaves as for RoundingMode.DOWN
. Note
that this rounding mode never decreases the calculated value.
Example:
Input Number  Input rounded to one digit with CEILING rounding


5.5  6 
2.5  3 
1.6  2 
1.1  2 
1.0  1 
1.0  1 
1.1  1 
1.6  1 
2.5  2 
5.5  5 
public static final RoundingMode FLOOR
RoundingMode.DOWN
;
if negative, behave as for RoundingMode.UP
. Note that
this rounding mode never increases the calculated value.
Example:
Input Number  Input rounded to one digit with FLOOR rounding


5.5  5 
2.5  2 
1.6  1 
1.1  1 
1.0  1 
1.0  1 
1.1  2 
1.6  2 
2.5  3 
5.5  6 
public static final RoundingMode HALF_UP
RoundingMode.UP
if the discarded
fraction is ≥ 0.5; otherwise, behaves as for
RoundingMode.DOWN
. Note that this is the rounding
mode commonly taught at school.
Example:
Input Number  Input rounded to one digit with HALF_UP rounding


5.5  6 
2.5  3 
1.6  2 
1.1  1 
1.0  1 
1.0  1 
1.1  1 
1.6  2 
2.5  3 
5.5  6 
public static final RoundingMode HALF_DOWN
RoundingMode.UP
if the discarded
fraction is > 0.5; otherwise, behaves as for
RoundingMode.DOWN
.
Example:
Input Number  Input rounded to one digit with HALF_DOWN rounding


5.5  5 
2.5  2 
1.6  2 
1.1  1 
1.0  1 
1.0  1 
1.1  1 
1.6  2 
2.5  2 
5.5  5 
public static final RoundingMode HALF_EVEN
RoundingMode.HALF_UP
if the digit to the left of the
discarded fraction is odd; behaves as for
RoundingMode.HALF_DOWN
if it's even. Note that this
is the rounding mode that statistically minimizes cumulative
error when applied repeatedly over a sequence of calculations.
It is sometimes known as "Banker's rounding," and is
chiefly used in the USA. This rounding mode is analogous to
the rounding policy used for float
and double
arithmetic in Java.
Example:
Input Number  Input rounded to one digit with HALF_EVEN rounding


5.5  6 
2.5  2 
1.6  2 
1.1  1 
1.0  1 
1.0  1 
1.1  1 
1.6  2 
2.5  2 
5.5  6 
public static final RoundingMode UNNECESSARY
ArithmeticException
is thrown.
Example:
Input Number  Input rounded to one digit with UNNECESSARY rounding


5.5  throw ArithmeticException 
2.5  throw ArithmeticException 
1.6  throw ArithmeticException 
1.1  throw ArithmeticException 
1.0  1 
1.0  1 
1.1  throw ArithmeticException 
1.6  throw ArithmeticException 
2.5  throw ArithmeticException 
5.5  throw ArithmeticException 
public static RoundingMode[] values()
for (RoundingMode c : RoundingMode.values()) System.out.println(c);
public static RoundingMode valueOf(String name)
name
 the name of the enum constant to be returned.IllegalArgumentException
 if this enum type has no constant with the specified nameNullPointerException
 if the argument is nullpublic static RoundingMode valueOf(int rm)
RoundingMode
object corresponding to a
legacy integer rounding mode constant in BigDecimal
.rm
 legacy integer rounding mode to convertRoundingMode
corresponding to the given integer.IllegalArgumentException
 integer is out of range