格式化爲小數點後兩位和1位sig圖

Question

我試圖將一個double格式化爲兩位小數和1位sig字符串。我的代碼到目前爲止，我是否正確地做？或者我不應該創建一個臨時字符串？...

// sets rounding to two decimal places 
DecimalFormat format_calculated_reported_concentration = new DecimalFormat("0.00"); 

// removes grouping seperators e.g. 1,000 becomes 1000 
format_calculated_reported_concentration.setGroupingUsed(false); 

/// rounds 
String temp_calculated_reported_concentration = 
     format_calculated_reported_concentration.format(calculated_concentration); 

// applies the pattern of 1 significant figure only to the decimalformat 
format_calculated_reported_concentration.applyPattern("@"); 

// 1 sig fig 
calculated_reported_concentration = 
     format_calculated_reported_concentration 
      .format(Double.valueOf(temp_calculated_reported_concentration)); 

Answer 1

這不工作嗎？

// sets rounding to two decimal places 
DecimalFormat format_calculated_reported_concentration = new DecimalFormat("0.00"); 

// removes grouping seperators e.g. 1,000 becomes 1000 
format_calculated_reported_concentration.setGroupingUsed(false); 

// applies the pattern of 1 significant figure only to the decimalformat 
format_calculated_reported_concentration.applyPattern("@"); 

// 1 sig fig 
calculated_reported_concentration = 
     format_calculated_reported_concentration 
      .format(calculated_concentration); 

你也可以設立DecimalFormat一次，就像在一個構造函數或初始化程序，而不是每次你做的格式化時間。