如何將答案四舍五入到小數點后兩位

Question

我有一個簡單的數學示例“加，減，除和乘”，並且將變量用作雙精度，並且如果我使用小數來加減或除，則答案應該在小數點后兩位。

    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));
    }                                              

如何獲取結果舍入到小數點后兩位，例如12.38而不是12.379999

Answer 1

使用setRoundingMode告訴它您想要多少個小數點。

Answer 2

你可以這樣做

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

number是您的十進制數字

分解-

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

輸出將是3.14