Java reserved two-bit decimals and JS reserved two-bit decimal consistency study

One, Java reserved two-bit decimal way

 Public Static voidMain (string[] args) {System.out.println ("=======decimalformat (rounding, five into possible failure) ========="); DecimalFormat DecimalFormat=NewDecimalFormat ("0.00"); System.out.println (Decimalformat.format (0.235));//0.23System.out.println (Decimalformat.format (1.235));//1.24System.out.println ("=======string.format (rounded) ========="); System.out.println (String.Format ("%.2f", 0.235));//0.24System.out.println (String.Format ("%.2f", 1.235));//1.24System.out.println ("=======numberformat (rounding, five into possible failure) ========="); NumberFormat NF=numberformat.getnumberinstance (); Nf.setmaximumfractiondigits (2); System.out.println (Nf.format (0.235));//0.23System.out.println (Nf.format (1.235));//1.24System.out.println ("=======bigdecimal (Specify rounding mode, constructors use string type to calculate accurately) ========="); System.out.println ("Round_half_down: Five five Points 1 in."); //BigDecimal BigDecimal = new BigDecimal (1.235);//use the double type directly to calculate the wrong//System.out.println (Bigdecimal.setscale (2,bigdecimal.round_half_down). Doublevalue ());BigDecimal BigDecimal=NewBigDecimal (String.valueof (0.235)); System.out.println (Bigdecimal.setscale (2,bigdecimal.round_half_down). Doublevalue ());//0.23BigDecimal=NewBigDecimal (1.235+ ""); System.out.println (Bigdecimal.setscale (2,bigdecimal.round_half_down). Doublevalue ());//1.23BigDecimal=NewBigDecimal (1.2351+ ""); System.out.println (Bigdecimal.setscale (2,bigdecimal.round_half_down). Doublevalue ());//1.24System.out.println ("Round_half_up: Rounding"); //bigDecimal = new BigDecimal (0.235);//use the double type directly to calculate the wrong//System.out.println (Bigdecimal.setscale (2,bigdecimal.round_half_up). Doublevalue ());BigDecimal=NewBigDecimal (String.valueof (0.235)); System.out.println (Bigdecimal.setscale (2,BIGDECIMAL.ROUND_HALF_UP). Doublevalue ());//0.24BigDecimal=NewBigDecimal (1.235+ ""); System.out.println (Bigdecimal.setscale (2,BIGDECIMAL.ROUND_HALF_UP). Doublevalue ());//1.24}

Results

=======decimalformat (rounded, five into possible failure) =========0.231.24=======string.format (rounded) =========0.241.24======= NumberFormat (rounding, five into possible failure) =========0.231.24=======bigdecimal (Specify rounding mode, constructors use string type to calculate accurately) =========round_half_ Down: Five five points 1 into 0.231.231.24round_half_up: Rounding 0.241.24

Second, JS reserved two decimal places

0.235.toFixed (2); 0.231.235.toFixed (2); 1.24

Summarize:

1.js.tofixed Way and Java DecimalFormat and numberformat the same way, the results are uncertain, four five may not enter!

2.java can be accurate 455 into the String.Format mode and the BigDecimal mode of ROUND_HALF_UP, but you must ensure that the BigDecimal construction parameter is a string type, otherwise there will be five phenomenon.

3.js exact Rounding implementation method, the online find example, as follows

function (fractiondigits)  {      // does not do any processing on fractiondigits, assuming it is a  valid input    return ( parseint (this * MATH.POW (Ten, fractiondigits  ) + 0.5)/math.pow (10,fractiondigts)). toString ();    

Therefore, if the front and rear table calculation is consistent, there are the following scenarios

Front	Background	Results
ToFixed	DecimalFormat or NumberFormat	Inaccurate rounding, but consistent results
The improved tofixed	BigDecimal using ROUND_HALF_UP mode	Exactly 455, and the results are consistent.

Because of the diversity of browsers, the infinite nature of the data, not too much testing, this is only a preliminary conclusion. It is best to make sure that it is foolproof or a computational party!

Java reserved two-bit decimals and JS reserved two-bit decimal consistency study