JDK 8 code review request for 6964528: Double.toHexString(double d) String manipulation with + in an append of StringBuilder

[Louis Wasserman]

Would appending the character 'p' instead of the string "p" make any
difference?


On Fri, Feb 1, 2013 at 1:39 PM, Joe Darcy <joe.darcy at oracle.com> wrote:

> Hello,
>
> Please review a simple refactoring fix in Double.toHexString
>
>     6964528: Double.toHexString(double d) String manipulation with + in an
> append of StringBuilder
>     http://cr.openjdk.java.net/~**darcy/6964528.0/<http://cr.openjdk.java.net/~darcy/6964528.0/>
>
> Patch below.
>
> Thanks,
>
> -Joe
>
> --- old/src/share/classes/java/**lang/Double.java    2013-02-01
> 13:36:33.000000000 -0800
> +++ new/src/share/classes/java/**lang/Double.java    2013-02-01
> 13:36:33.000000000 -0800
> @@ -1,5 +1,5 @@
>  /*
> - * Copyright (c) 1994, 2012, Oracle and/or its affiliates. All rights
> reserved.
> + * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights
> reserved.
>   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
>   *
>   * This code is free software; you can redistribute it and/or modify it
> @@ -289,7 +289,7 @@
>              return Double.toString(d);
>          else {
>              // Initialized to maximum size of output.
> -            StringBuffer answer = new StringBuffer(24);
> +            StringBuilder answer = new StringBuilder(24);
>
>              if (Math.copySign(1.0, d) == -1.0)    // value is negative,
>                  answer.append("-");                  // so append sign
> info
> @@ -300,8 +300,7 @@
>
>              if(d == 0.0) {
>                  answer.append("0.0p0");
> -            }
> -            else {
> +            } else {
>                  boolean subnormal = (d < DoubleConsts.MIN_NORMAL);
>
>                  // Isolate significand bits and OR in a high-order bit
> @@ -324,13 +323,14 @@
>                                "0":
>                                signif.replaceFirst("0{1,12}$"**, ""));
>
> +                answer.append("p");
>                  // If the value is subnormal, use the E_min exponent
>                  // value for double; otherwise, extract and report d's
>                  // exponent (the representation of a subnormal uses
>                  // E_min -1).
> -                answer.append("p" + (subnormal ?
> -                               DoubleConsts.MIN_EXPONENT:
> -                               Math.getExponent(d) ));
> +                answer.append(subnormal ?
> +                              DoubleConsts.MIN_EXPONENT:
> +                              Math.getExponent(d));
>              }
>              return answer.toString();
>          }
>
>


-- 
Louis Wasserman