RoundingMode

java.lang.Object
- java.lang.Enum<RoundingMode>
- - java.math.RoundingMode

所有已实现的接口:: Serializable, Comparable<RoundingMode>

public enum RoundingMode
extends 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 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 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 BigDecimal#round on this number with the proper 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	`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 integer-based enumeration of rounding mode constants in BigDecimal (BigDecimal#ROUND_UP, BigDecimal#ROUND_DOWN, etc. ).

从以下版本开始:: 1.5
另请参阅:: BigDecimal, MathContext

枚举常量概要

枚举常量
枚举常量	说明
`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.

方法概要

所有方法静态方法具体方法
限定符和类型	方法	说明
`static RoundingMode`	`valueOf(int rm)`	Returns the `RoundingMode` object corresponding to a legacy integer rounding mode constant in `BigDecimal`.
`static RoundingMode`	`valueOf(String name)`	返回带有指定名称的该类型的枚举常量。字符串必须与用于声明该类型的枚举常量的标识符完全匹配。(不允许有多余的空格字符。)
`static RoundingMode[]`	`values()`	按照声明该枚举类型的常量的顺序, 返回包含这些常量的数组。该方法可用于迭代常量, 如下所示: for (RoundingMode c : RoundingMode.values()) System.out.println(c);

从类继承的方法 java.lang.Enum
clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

从类继承的方法 java.lang.Object
getClass, notify, notifyAll, wait, wait, wait

枚举常量详细资料

UP
```
public static final RoundingMode UP
```
Rounding mode to round away from zero. Always increments the digit prior to a non-zero discarded fraction. Note that this rounding mode never decreases the magnitude of the calculated value.
Example:
Rounding mode UP Examples
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

**Rounding mode UP Examples**
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

DOWN
```
public static final 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:
Rounding mode DOWN Examples
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

**Rounding mode DOWN Examples**
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

CEILING
```
public static final RoundingMode CEILING
```
Rounding mode to round towards positive infinity. If the result is positive, behaves as for RoundingMode.UP; if negative, behaves as for RoundingMode.DOWN. Note that this rounding mode never decreases the calculated value.
Example:
Rounding mode CEILING Examples
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

**Rounding mode CEILING Examples**
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

FLOOR
```
public static final RoundingMode FLOOR
```
Rounding mode to round towards negative infinity. If the result is positive, behave as for RoundingMode.DOWN; if negative, behave as for RoundingMode.UP. Note that this rounding mode never increases the calculated value.
Example:
Rounding mode FLOOR Examples
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

**Rounding mode FLOOR Examples**
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

HALF_UP
```
public static final RoundingMode HALF_UP
```
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round up. Behaves as for 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:
Rounding mode HALF_UP Examples
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

**Rounding mode HALF_UP Examples**
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

HALF_DOWN
```
public static final RoundingMode HALF_DOWN
```
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round down. Behaves as for RoundingMode.UP if the discarded fraction is > 0.5; otherwise, behaves as for RoundingMode.DOWN.
Example:
Rounding mode HALF_DOWN Examples
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

**Rounding mode HALF_DOWN Examples**
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

HALF_EVEN
```
public static final RoundingMode HALF_EVEN
```
Rounding mode to round towards the "nearest neighbor" unless both neighbors are equidistant, in which case, round towards the even neighbor. Behaves as for 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:
Rounding mode HALF_EVEN Examples
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

**Rounding mode HALF_EVEN Examples**
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

UNNECESSARY

public static final 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 ArithmeticException is thrown.

Example:

**Rounding mode UNNECESSARY Examples**
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`

方法详细资料
- values
```
public static RoundingMode[] values()
```
  按照声明该枚举类型的常量的顺序, 返回包含这些常量的数组。该方法可用于迭代常量, 如下所示:
```
for (RoundingMode c : RoundingMode.values())
    System.out.println(c);
```
  返回:
  
  按照声明该枚举类型的常量的顺序返回的包含这些常量的数组
- valueOf
```
public static RoundingMode valueOf(String name)
```
  返回带有指定名称的该类型的枚举常量。字符串必须与用于声明该类型的枚举常量的标识符完全匹配。(不允许有多余的空格字符。)
  
  参数:
  
  name - 要返回的枚举常量的名称。
  
  返回:
  
  返回带有指定名称的枚举常量
  
  抛出:
  
  IllegalArgumentException - 如果该枚举类型没有带有指定名称的常量
  
  NullPointerException - 如果参数为空值
- valueOf
```
public static RoundingMode valueOf(int rm)
```
  Returns the RoundingMode object corresponding to a legacy integer rounding mode constant in BigDecimal.
  
  参数:
  
  rm - legacy integer rounding mode to convert
  
  返回:
  
  RoundingMode corresponding to the given integer.
  
  抛出:
  
  IllegalArgumentException - integer is out of range

枚举 RoundingMode

枚举常量概要

方法概要

从类继承的方法 java.lang.Enum

从类继承的方法 java.lang.Object

枚举常量详细资料

UP

DOWN

CEILING

FLOOR

HALF_UP

HALF_DOWN

HALF_EVEN

UNNECESSARY

方法详细资料

values

valueOf

valueOf