java中Double转为String时不以科学计数法显示

问题：
当Double的长度超过一定长度的时候，会以科学计数法显示。对于前段显示不是很友好。因此需要将其转化为原样式显示。

下面以前端显示金额为例，保留2位小数

1. 最佳方法

   Double num = 123000000.456d;//1.23000000456E8
   //按照原样
   String str = new BigDecimal(Double.toString(num)).toPlainString();//123000000.456
   //按照四舍五入方式保留2位小数
   String str2 = new BigDecimal(Double.toString(num)).setScale(2, RoundingMode.HALF_UP).toString();//123000000.46
   

2. 分析过程

   
   public class DoubleTest {
   
       private static void doubleTest1() {
           Double d = 123.000;
           System.out.println(d.toString());//123.0
           System.out.println(d.longValue());//123
           System.out.println(String.valueOf(d));//123.0
           System.out.println(Double.toString(d));//123.0
           System.out.println(new BigDecimal(d));//123
           System.out.println(new BigDecimal(Double.toString(d)).toString());//123.0
           System.out.println(new BigDecimal(Double.toString(d)).setScale(2, RoundingMode.HALF_UP).toString());//123.00
           System.out.println(new DecimalFormat("0.00").format(d));//123.00
           System.out.println(doubleToString(d));//123
   
   
           Double d2 = 123.456;
           System.out.println(d2.toString());//123.456
           System.out.println(d2.longValue());//123
           System.out.println(String.valueOf(d2));//123.456
           System.out.println(Double.toString(d2));//123.456
           System.out.println(new BigDecimal(d2));//123.4560000000000030695446184836328029632568359375
           System.out.println(new BigDecimal(Double.toString(d2)).toString());//123.456
           System.out.println(new BigDecimal(Double.toString(d2)).setScale(2, RoundingMode.HALF_UP).toString());//123.46
           System.out.println(new DecimalFormat("0.00").format(d2));//123.46
           System.out.println(doubleToString(d2));//123.46
       }
   
       private static void doubleTest2() {
           Double d = 123000000000.000;
           System.out.println(d.toString());//1.23E11
           System.out.println(d.longValue());//123000000000
           System.out.println(String.valueOf(d));//1.23E11
           System.out.println(Double.toString(d));//1.23E11
           System.out.println(new BigDecimal(d));//123000000000
           System.out.println(new BigDecimal(d).setScale(2));//123000000000.00
           System.out.println(new BigDecimal(Double.toString(d)).toString());//1.23E+11
           System.out.println(new BigDecimal(Double.toString(d)).setScale(2, RoundingMode.HALF_UP).toString());//123000000000.00
           System.out.println(new DecimalFormat("0.00").format(d));//123000000000.00
           System.out.println(doubleToString(d));//123000000000
   
   
           Double d2 = 123000000000.456;
           System.out.println(d2.toString());//1.23000000000456E11
           System.out.println(d2.longValue());//123000000000
           System.out.println(String.valueOf(d2));//1.23000000000456E11
           System.out.println(Double.toString(d2));//1.23000000000456E11
           System.out.println(new BigDecimal(d2));//123000000000.45599365234375
           System.out.println(new BigDecimal(d).setScale(2).toString());//123000000000.00
           System.out.println(new BigDecimal(Double.toString(d2)).toString());//123000000000.456
           System.out.println(new BigDecimal(Double.toString(d2)).setScale(2, RoundingMode.HALF_UP).toString());//123000000000.46
           System.out.println(new DecimalFormat("0.00").format(d2));//123000000000.46
           System.out.println(doubleToString(d2));//123000000000.46
   
       }
   
       /**
        * doubleToString
        */
   
       private static String doubleToString(Double d) {
           NumberFormat nf = NumberFormat.getInstance();
           //四舍五入
           nf.setRoundingMode(RoundingMode.HALF_UP);
           //取消遇到3位就加','，如1230，表示为1,230
           nf.setGroupingUsed(false);
           //最大小数位
           nf.setMaximumFractionDigits(2);
           return nf.format(d);
       }
   }