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 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
{@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 integerbased
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 

public RoundingMode  UP  Rounding mode to round away from zero. Always increments the
digit prior to a nonzero discarded fraction. Note that this
rounding mode never decreases the magnitude of the calculated
value.
Example:
Input Number 
Input rounded to one digit with {@code 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 RoundingMode  DOWN  Rounding mode to round towards zero. Never increments the digit
prior to a discarded fraction (i.e., truncates). Note that this
rounding mode never increases the magnitude of the calculated value.
Example:
Input Number 
Input rounded to one digit with {@code 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 RoundingMode  CEILING  Rounding mode to round towards positive infinity. If the
result is positive, behaves as for {@code RoundingMode.UP};
if negative, behaves as for {@code RoundingMode.DOWN}. Note
that this rounding mode never decreases the calculated value.
Example:
Input Number 
Input rounded to one digit with {@code 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 RoundingMode  FLOOR  Rounding mode to round towards negative infinity. If the
result is positive, behave as for {@code RoundingMode.DOWN};
if negative, behave as for {@code RoundingMode.UP}. Note that
this rounding mode never increases the calculated value.
Example:
Input Number 
Input rounded to one digit with {@code 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 RoundingMode  HALF_UP  Rounding mode to round towards {@literal "nearest neighbor"}
unless both neighbors are equidistant, in which case round up.
Behaves as for {@code RoundingMode.UP} if the discarded
fraction is ≥ 0.5; otherwise, behaves as for
{@code RoundingMode.DOWN}. Note that this is the rounding
mode commonly taught at school.
Example:
Input Number 
Input rounded to one digit with {@code 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 RoundingMode  HALF_DOWN  Rounding mode to round towards {@literal "nearest neighbor"}
unless both neighbors are equidistant, in which case round
down. Behaves as for {@code RoundingMode.UP} if the discarded
fraction is > 0.5; otherwise, behaves as for
{@code RoundingMode.DOWN}.
Example:
Input Number 
Input rounded to one digit with {@code 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 RoundingMode  HALF_EVEN  Rounding mode to round towards the {@literal "nearest neighbor"}
unless both neighbors are equidistant, in which case, round
towards the even neighbor. Behaves as for
{@code RoundingMode.HALF_UP} if the digit to the left of the
discarded fraction is odd; behaves as for
{@code 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 {@literal "Banker's rounding,"} and is
chiefly used in the USA. This rounding mode is analogous to
the rounding policy used for {@code float} and {@code double}
arithmetic in Java.
Example:
Input Number 
Input rounded to one digit with {@code 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 RoundingMode  UNNECESSARY  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} 

public final int  oldMode  
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 . 