RFR : 8013528 : (XS) Provide SharedSecrets access to String(char[], boolean) constructor (original) (raw)

Peter Levart peter.levart at gmail.com
Wed May 1 06:41:18 UTC 2013

Hi Mike,

Some comments about the test...

40 String benchmark = "exemplar"; 41 String constructorCopy = new String(benchmark); 42 String jlaCopy = jla.newStringUnsafe(benchmark.toCharArray()); 43 44 if (constructorCopy == constructorCopy) { 45 throw new Error("should be different instances"); 46 }

Wouldn't this always throw error? You really wanted to test benchmark == constructorCopy, right? 47 if (!benchmark.equals(constructorCopy)) { 48 throw new Error("Copy not equal"); 49 } 50 if (0 != Objects.compare(benchmark, constructorCopy, Comparators.naturalOrder())) { 51 throw new Error("Copy not equal"); 52 } 53 54 if (benchmark == jlaCopy) { 55 throw new Error("should be different instances"); 56 } 57 if (!benchmark.equals(jlaCopy)) { 58 throw new Error("Copy not equal"); 59 } 60 if (0 != Objects.compare(benchmark, jlaCopy, Comparators.naturalOrder())) { 61 throw new Error("Copy not equal"); 62 } 63 64 if (constructorCopy == jlaCopy) { 65 throw new Error("should be different instances"); 66 } 67 if (!constructorCopy.equals(jlaCopy)) { 68 throw new Error("Copy not equal"); 69 } 70 if (0 != Objects.compare(constructorCopy, jlaCopy, Comparators.naturalOrder())) { 71 throw new Error("Copy not equal");

To check whether the jlaCopy is really taking the given char array by reference, a test could also do something "illegal" like:

char[] array = benchmark.toCharArray();

String jlaCopy = jla.newStringUnsafe(array);

array[0] = "X"; // ouch!

String constructorCopy = new String(array);

if (!constructorCopy.equals(jlaCopy)) { ... }

Regards, Peter

2013/5/1 Mike Duigou <mike.duigou at oracle.com>

Hello all;

Since this code will be introduced without any usages I decided it was critical to make a stand alone unit test. I've updated the webrev: http://cr.openjdk.java.net/~mduigou/JDK-8013528/1/webrev/ The webrev mistakes my hg copy for a rename... Ignore that. Capturing the provenance of the test file probably isn't critical since the file is repurposed for a different test, but I prefer to have the origin tracked rather than use a non-vcs copy. I also made the other changes suggested by reviewers. Thanks Mike On Apr 29 2013, at 21:30 , Mike Duigou wrote: > Hello all; > > This change originated as part of JDK-8006627 (which was also previously split into JDK-8007398 as well). It adds an internal mechanism for performance sensitive usages to create a string from a provided character array without copying that array. This saves both in the allocation (and subsequent GC) as well as the copying of the characters. There are a few places in the JDK that return Strings which can benefit from this change. > > http://cr.openjdk.java.net/~mduigou/JDK-8013528/0/webrev/ > > Fear not, JDK-8006627 and JDK-8007398 will be revisited... For now it would be to get this change in to allow other potential users to move forward with their changes. > > Mike

More information about the core-libs-dev mailing list