乘法错误 [英] multiplication error

问题描述

如果我乘12×25.4我得到304.7，而我期望304.8。我看到使用单数x 25.4我得到正确的答案，但使用偶数似乎总是由0.1处于关机状态。我写这主要是基于公式，使任何见解将是有益的科学应用。

 如果（（（m1_sqs1_spinner.getSelectedItem（）。的toString（）。等于（IN））））    {//开始平方英寸
         双m1_sqs1_eng =新的双（m1_sqs1.getText（）的toString（））;         双square_effective_dia_inch = m1_sqs1_eng;         双square_effective_dia_mm = square_effective_dia_inch * 25.4;
         m1_ed_mm.setText（Double.toString（square_effective_dia_mm））;    } //在结束英寸正方形
 

解决方案

在Java的浮点数类型为近似值。试着增加1 + 2 + 3 + 4为浮动键入，你可能最终与10.00000003。

要确保精确的数学，请尝试使用的java.math.BigDecimal 键入。这是一个内存猪，但准确的。

If I multiply 12 x 25.4 i get 304.7 whereas I expect 304.8. I see that using odd numbers x 25.4 I get the correct answers but using even numbers always seem to be off by 0.1. I am writing a scientific app that is heavily based on formulas so any insight would be helpful.

if (((m1_sqs1_spinner.getSelectedItem().toString().equals("in"))))  

    { // start square in inches
         double m1_sqs1_eng = new Double(m1_sqs1.getText().toString()); 

         double square_effective_dia_inch = m1_sqs1_eng;

         double square_effective_dia_mm = square_effective_dia_inch * 25.4;
         m1_ed_mm.setText(Double.toString(square_effective_dia_mm));

    } // end square in inches

解决方案

Floating point number types in Java are approximations. Try adding 1 + 2 + 3 + 4 as float type and you might end up with 10.00000003.

To ensure accurate math, try using the java.math.BigDecimal type. It is a memory hog, but is accurate.

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