如何将答案四舍五入到小数点后两位

Question

我有一个简单的数学示例“加，减，除和乘”，并且将变量用作双精度，并且如果我使用小数来加减或除，则答案应该在小数点后两位。

    private void jButton_addActionPerformed(java.awt.event.ActionEvent  
    evt)    {                                            

    double First = Double.parseDouble(jTextField1.getText());
    // Read the Second number
    double Second = Double.parseDouble(jTextField2.getText());
    // Set the Result
    double Result = First + Second;

    jLabel4.setText(String.valueOf(Result));
     }                                           

    private void jButton_substractActionPerformed
   (java.awt.event.ActionEvent evt)   
   {                                                  

    double First = Double.parseDouble(jTextField1.getText());
   // Read the Second number
   double Second = Double.parseDouble(jTextField2.getText());
   // Set the Result
   double Result = First - Second;


   jLabel4.setText(String.valueOf(Result));
   }                                                 

    private void jButton_MultiplyActionPerformed  
   (java.awt.event.ActionEvent  evt)   
   {                                                 

    double First = Double.parseDouble(jTextField1.getText());
    // Read the Second number
    double Second = Double.parseDouble(jTextField2.getText());
    // Set the Result
    double Result = First * Second;


    jLabel4.setText(String.valueOf(Result));

  }                                                

   private void jButton_divideActionPerformed(java.awt.event.ActionEvent 
    evt)   {                                               

    double First = Double.parseDouble(jTextField1.getText());
    // Read the Second number
    double Second = Double.parseDouble(jTextField2.getText());
    // Set the Result
    double Result = First / Second;


    jLabel4.setText(String.valueOf(Result));
    }                                              

如何获取结果舍入到小数点后两位，例如12.38而不是12.379999

Answer 1

使用setRoundingMode告诉它您想要多少个小数点。

Answer 2

你可以这样做

double round = Math.round(number * 100.0) / 100.0;

number是您的十进制数字

分解-

double number = 3.14159;
number = Math.round(number * 100);
number = number/100;

输出将是3.14