hg: lambda/lambda/jdk: 2 new changesets

[Roel Spilker]

I understand the need, and give feedback on the implementation, assuming
the current API.

Feedback on the implementation of StringJoiner.java

1) The field `nullOutput` could become a constant, since there it is never
written to:
private static final String NULL_OUTPUT = "null";

2) There is no need for the field `nullOutputChars`. It is only used once,
in add(char[]) . This could easily be rewritten to:

public StringJoiner add(char[] newElement) {
prepareBuilder();
if (newElement == null) {
value.add(NULL_OUTPUT);
} else {
value.add(newElement);
}
return this;
}

3) `toString` calls `emptyOutput.toString()`. There is no need for that; it
is already a String.

4) The field `prefixLen` can be removed entirely. It is only used in
prepareBuilder the first time something is added. Actually, I think that
the code `if (prefixLen > 0)` can be ommitted at all, but at least it can
be replaced by `if (prefix.length() > 0)`

5) In `subSequence`, instead of creating a StringBuilder using the
CharSequence constructor, I think it is better to create a StringBuilder of
the right size and then append the subSequences of the `value` and `suffix`:

if (start < value.length()) {
return new StringBuilder(end - start)
.append(value.subSequence( start, value.length()))
.append(suffix.subSequence( 0, end - value.length());
}

6) In the constructor, in the common case there is no need for String
concatenation:
this.emptyOutput = this.suffix.isEmpty() ? this.prefix : this.prefix +
this.suffix;

7) `asChars`, `asCharArray` and `asCodePoints` be made much simpler by
calling toString (or a private method toStringInternal, ontaining the
current toString implementation, since a subclass might have overridden
toString) and than delegate the call:

public Iterable<Character> asChars() {
return toStringInternal().asChars();
}

public char[] asCharArray() {
return toStringInternal().asCharArray();
}

public Iterable<Integer> asCodePoints() {
return toStringInternal().asCodePoints();
}

This also takes care of the current inconsistencies beween `asCharArray`
and the other two methods.

8) Possibly get rid of the `prefix` field by adding it directly to the
`value` field in the constructor:

String prefixValue = prefix.toString();
this.emptyOutput = this.suffix.isEmpty() ? prefixValue : prefixValue +
this.suffix;
this.value = new StringBuilder().append(prefixValue);

On all code paths, the field `somethingAdded` is checked before reading the
`value` field.

The method `prepareBuilder` would then become:

if (!somethingAdded) {
somethingAdded = true;
} else {
value.append(infix);
}

Removing the field is obviously a good thing. The downside is that the
contents of the prefix is now always copied to the `value` field, even when
no actual values are added. Then again, I expect the prefix to be empty in
most of the use cases.

Roel


On Mon, Jun 25, 2012 at 4:29 PM, Brian Goetz <brian.goetz at oracle.com> wrote:

> This is a reasonable place for such feedback.
>
> The motivation for StringJoiner was twofold:
>  - to address the long-standing RFE for String.join;
>  - to provide an easy means of joining a stream of strings (e.g., names =
> people.map(Person::getName).**into(new StringJoiner(", "))
>
>
>
>
> On 6/25/2012 7:56 AM, Roel Spilker wrote:
>
>> I have some feedback on the implementation of StringJoiner. Where and how
>> can I give this feedback?
>>
>> Roel
>>
>> On Sat, Jun 23, 2012 at 3:10 AM,<stuart.marks at oracle.com>  wrote:
>>
>>  Changeset: 915296b3c16e
>>> Author:    jgish
>>> Date:      2012-06-20 18:40 -0400
>>> URL:       http://hg.openjdk.java.net/**lambda/lambda/jdk/rev/**
>>> 915296b3c16e<http://hg.openjdk.java.net/lambda/lambda/jdk/rev/915296b3c16e>
>>>
>>> 5015163: (str) String merge/join that is the inverse of String.split()
>>> Summary: Convenience methods on String to access the
>>> java.util.StringJoiner functionality
>>> Reviewed-by: smarks, briangoetz
>>>
>>> ! src/share/classes/java/lang/**AbstractStringBuilder.java
>>> ! src/share/classes/java/lang/**String.java
>>> ! src/share/classes/java/lang/**StringBuffer.java
>>> ! src/share/classes/java/lang/**StringBuilder.java
>>> ! src/share/classes/java/util/**StringJoiner.java
>>> ! test-ng/tests/org/openjdk/**tests/java/lang/StringTest.**java
>>> ! test-ng/tests/org/openjdk/**tests/java/util/**FillableStringTest.java
>>> ! test-ng/tests/org/openjdk/**tests/java/util/**StringJoinerTest.java
>>>
>>> Changeset: 7af64c20ebe7
>>> Author:    smarks
>>> Date:      2012-06-22 18:12 -0700
>>> URL:       http://hg.openjdk.java.net/**lambda/lambda/jdk/rev/**
>>> 7af64c20ebe7<http://hg.openjdk.java.net/lambda/lambda/jdk/rev/7af64c20ebe7>
>>>
>>> merge
>>>
>>>
>>>
>>>
>>>
>>