
Java™ Platform Standard Ed. 6 

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java.lang.Object java.lang.Enum<RoundingMode> java.math.RoundingMode
public enum 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
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 Summary  

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. 
Method Summary  

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. 
Methods inherited from class java.lang.Enum 

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf 
Methods inherited from class java.lang.Object 

getClass, notify, notifyAll, wait, wait, wait 
Enum Constant Detail 

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
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
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
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
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
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
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 
Method Detail 

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 name
NullPointerException
 if the argument is nullpublic static RoundingMode valueOf(int rm)
BigDecimal
.
rm
 legacy integer rounding mode to convert
IllegalArgumentException
 integer is out of range

Java™ Platform Standard Ed. 6 

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Copyright 2006 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.