RFR (JDK11) 8137326: Methods for comparing CharSequence, StringBuilder, and StringBuffer

[Joe Wang]

Hi Tagir,

Thanks for the comment. I will consider adding that to the javadoc 
emphasizing that the comparison is performed from 0 to length() - 1 of 
the two sequences.

Best,
Joe

On 1/29/18, 8:07 PM, Tagir Valeev wrote:
> Hello!
>
> An AbstractStringBuilder#compareTo implementation is wrong. You cannot
> simply compare the whole byte array. Here's the test-case:
>
> public class Test {
>    public static void main(String[] args) {
>      StringBuilder sb1 = new StringBuilder("test1");
>      StringBuilder sb2 = new StringBuilder("test2");
>      sb1.setLength(4);
>      sb2.setLength(4);
>      System.out.println(sb1.compareTo(sb2));
>      System.out.println(sb1.toString().compareTo(sb2.toString()));
>    }
> }
>
> We truncated the stringbuilders making their content equal, so
> sb1.toString().compareTo(sb2.toString()) is 0, but compareTo compares
> the original content (before the truncation) as truncation, of course,
> does not zero the truncated bytes, neither does it reallocate the
> array (unless explicitly asked via trimToSize).
>
> With best regards,
> Tagir Valeev.
>
>
> On Fri, Jan 26, 2018 at 10:00 AM, Joe Wang<huizhe.wang at oracle.com>  wrote:
>> Hi,
>>
>> Adding methods for comparing CharSequence, StringBuilder, and StringBuffer.
>>
>> The Comparable implementations for StringBuilder/Buffer are similar to that
>> of String, allowing comparison operations between two
>> StringBuilders/Buffers, e.g. aStringBuilder.compareTo(anotherStringBuilder).
>> For CharSequence however, refer to the comments in JIRA, a static method
>> 'compare' is added instead of implementing the Comparable interface. This
>> 'compare' method may take CharSequence implementations such as String,
>> StringBuilder and StringBuffer, making it possible to perform comparison
>> among them. The previous example for example is equivalent to
>> CharSequence.compare(aStringBuilder, anotherStringBuilder).
>>
>> Tests for java.base have been independent from each other. The new tests are
>> therefore created to have no dependency on each other or sharing any code.
>>
>> JBS: https://bugs.openjdk.java.net/browse/JDK-8137326
>> webrev: http://cr.openjdk.java.net/~joehw/jdk11/8137326/webrev/
>>
>> Thanks,
>> Joe