hg: jdk8/tl/jdk: 6924259: Remove offset and count fields from java.lang.String (original) (raw)

Zhong Yu zhong.j.yu at gmail.com
Thu Nov 8 17:22:03 UTC 2012

On 06/03/2012 11:35 PM, Mike Duigou wrote:

[I trimmed the distribution list]

On Jun 3 2012, at 13:44 , Peter Levart wrote:

On Thursday, May 31, 2012 03:22:35 AM mike.duigou at oracle.com wrote: Changeset: 2c773daa825d Author: mduigou Date: 2012-05-17 10:06 -0700 URL: http://hg.openjdk.java.net/jdk8/tl/jdk/rev/2c773daa825d

6924259: Remove offset and count fields from java.lang.String Summary: Removes the use of shared character array buffers by String along with the two fields needed to support the use of shared buffers. Wow, that's quite a change. Indeed. It was a long time in development. It is a change which is expected to be overall beneficial though and in the general case a positive win.

Wow!

If the previous behavior of substring() was once a bug, by now it has become a well known feature. People know about it, and people depend on it.

This change is a big surprise. Changing O(1) to O(n) is a breach of contract. It'll break lots of old code; and meanwhile lots of new code are still being written based on the old assumption. After people learned about the new behavior, they need to comb through and rewrite their code.

The worst part is the same code performs very differently on different versions of JDK. What's a programmer supposed to do if his code targets JDK6 and above? If the cost of strings are no longer certain, what else can we believe in?

Is there any chance in hell to roll it back? Maybe add a new method for the new behavior?

Zhong Yu

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