BigDecimal 除以不均匀小数

Question

我正在尝试开发一个程序来处理必要的多个 BigDecimal 计算。我处于相当混乱的状态，因为 BigDecimal 没有按照我的意愿进行合作。让我解释一下我需要它做什么：

首先它需要一个货币金额，最多可以有两位小数。然后它需要“分配”，这基本上是该金额将通过多少个帐户进行分配。

程序现在应该在账户之间分配金额。当然，在某些情况下，金额不能平均分配，例如 3.33 美元在 2 个帐户之间分配。在这种情况下，您必须有 1 个分配额外的美分或四舍五入。四舍五入不是一种选择，每一分钱都必须考虑在内。这是我到目前为止所拥有的：

totalAllocations = TransactionWizard.totalAllocations;//Set in another class, how many accounts total will be spread

    BigDecimal totalAllocationsBD = new BigDecimal(totalAllocations).setScale(2);//Converts to big decimal. 

    amountTotal = (BigDecimal) transInfo.get("amount"); // set total amount

    MathContext mc = new MathContext(2);
    remainderAllocation = amountTotal.remainder(totalAllocationsBD, mc);

    dividedAllocationAmount = amountTotal.divide(totalAllocationsBD, MathContext.DECIMAL32);

    dividedAllocationAmount=dividedAllocationAmount.setScale(2);

在课后，我实际上写了这些值。我首先有一个计数器，它设置为 totalAllocations。然后我有一个循环，它将写入一些信息，包括divideAllocationAmount。所以说总金额为 10，我有两次分配，那么 5.00 将被写入两次。

我想要的是对于总数不能在分配之间平均分配的情况，以便有一个额外的分配来保存剩余部分，如下所示：

if(remainderAllocation.compareTo(BigDecimal.ZERO) >0 && allocationCounter==1){
                adjAmt.setValue(remainderAllocation);
            }else{
                adjAmt.setValue(dividedAllocationAmount);
            }

adjAmt 只是设置一个 XML 字段，这是一个 JAXB 项目。

我在这里遇到的主要问题是带有余数的数字。例如，如果用户选择 2 个分配并且金额为 3.33 美元，那么程序将失败并给我一个舍入错误。

Exception in thread "AWT-EventQueue-0" java.lang.ArithmeticException: Rounding necessary
    at java.math.BigDecimal.commonNeedIncrement(Unknown Source)
    at java.math.BigDecimal.needIncrement(Unknown Source)
    at java.math.BigDecimal.divideAndRound(Unknown Source)
    at java.math.BigDecimal.setScale(Unknown Source)
    at java.math.BigDecimal.setScale(Unknown Source)
    at model.Creator.createTransaction(Creator.java:341)
    at view.TransactionWizard$2.actionPerformed(TransactionWizard.java:333)
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
    at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.processMouseEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Window.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$500(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.WaitDispatchSupport$2.run(Unknown Source)
    at java.awt.WaitDispatchSupport$4.run(Unknown Source)
    at java.awt.WaitDispatchSupport$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.awt.WaitDispatchSupport.enter(Unknown Source)
    at java.awt.Dialog.show(Unknown Source)
    at java.awt.Component.show(Unknown Source)
    at java.awt.Component.setVisible(Unknown Source)
    at java.awt.Window.setVisible(Unknown Source)
    at java.awt.Dialog.setVisible(Unknown Source)
    at view.MainView$15$1.run(MainView.java:398)
    at java.awt.event.InvocationEvent.dispatch(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$500(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)
Local Instrument: WEB

如果总金额为 10.51 美元并且有 3 个分配，也会发生同样的情况。实际上，我想要的是两次分配为 5.25 美元，第三次分配为 0.01 美元。 （因为那是余数）。我该怎么办？

Answer 1

当然在某些情况下金额不能平分， 例如 3.33 美元在 2 个帐户之间分配。在这种情况下，您必须 要么有 1 个分配额外的美分或四舍五入

[没有优化、最佳实践、错误处理、数据类型转换等普通工作伪代码。]

试试这个

        float amount = 3.33f;

        int allocations = 2;

        double average = amount/allocations;

        System.out.println("ACTUAL AVERAGE "+average);

        double rounded = Math.round(average * 100.0) / 100.0;

        System.out.println("ROUNDED VALUE: "+rounded);

        double adjustment = average - rounded;

        adjustment*=allocations; //-- FOR EACH ALLOCATION

        for(int i=1; i<allocations; i++){
            System.out.println("Allocation :" +i + " = "+rounded);
        }

        //-- ADDING ADJUSTED ROUNDING AMOUNT TO LAST ONE
        double adjustedAmount = Math.round((rounded+adjustment) * 100.0) / 100.0;

        System.out.println("Allocation :" +allocations +" = " + adjustedAmount);

数量为 3.33 的输出，有 2 个分配。

ACTUAL AVERAGE 1.6649999618530273
ROUNDED VALUE: 1.66
Allocation :1 = 1.66
Allocation :2 = 1.67 //-- EXTRA CENT

如果总金额为 10.51 美元并且有 3 个 分配。实际上，我想要的是两次分配 5.25 美元，第三次分配为 0.01 美元。 （因为那是 余）。我该怎么办？

现在这与你上面所说的不同，你可以有 3.5、3.5 和 3.51。

但是如果你想要单独的 0.01，那么改变上面的代码 allocations-1 并将余数设置为最后的分配。所以第 2 次分配为 5.25，第 3 次分配为 0.01，希望对您有所帮助。

Answer 2

通过自己的反复试验，我终于找到了解决这个问题的方法。事实证明，对我来说，关键是先取出余数，然后进行除法。

因为我知道我想根据情况自动将大十进制分成三部分，所以我这样做了..

package mathtest;

import java.math.BigDecimal;
import java.math.MathContext;
import java.math.RoundingMode;

public class MathTest 

{

    public static BigDecimal totalAmount;
    public static BigDecimal totalAllocations; 
    public static BigDecimal divisibleAmount;
    public static BigDecimal remainderAmount;
    public static BigDecimal subtractDecimal;


    public static void main(String args[]){

        MathContext mc = new MathContext(2);

        totalAmount = new BigDecimal(10.00).setScale(2,RoundingMode.HALF_UP);//Sets the total monetary amount. Standard monetary rounding. 
        totalAllocations = new BigDecimal(2);//The number of accounts the total amount will be split between. 
        subtractDecimal = new BigDecimal(1.00);//Used to remove one from the total allocations (to account for the remainder). 

        remainderAmount = totalAmount.remainder(totalAllocations, mc);//Gets the remainder assuming you tried to divide total/allocations. 

        totalAmount=totalAmount.subtract(remainderAmount);//Subtracts the remainder from the total. 


        if(remainderAmount.compareTo(BigDecimal.ZERO) >0){//If there is a remainder. 

        //The divisible amount is the total amount divided by the total allocations minus 1 (to account for remainder). 
        divisibleAmount=totalAmount.divide(totalAllocations.subtract(subtractDecimal));

        }else{//If there is no remainder 

            divisibleAmount=totalAmount.divide(totalAllocations);//The divisible amount is the total amount divided by the total allocations. 
        }
        if(remainderAmount.compareTo(BigDecimal.ZERO)>0){
        System.out.println(remainderAmount);    
        }


        //The below would be printed once for each allocation. 

        System.out.println(divisibleAmount);
    }

}