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    <p>Originally, this option was added to improve SPECjBB performance. The gains are due to reduced memory bandwidth requirements between the processor and DRAM. Loading and storing bytes in the byte[] consumes 1/2 the bandwidth versus chars in the char[].</p> <p>However, this comes at a price. The code has to determine if the internal array is a byte[] or char[]. This takes CPU time and if the workload is not memory <strong>bandwidth</strong> constrained, it can cause a performance regression. There is also a code maintenance price due to the added complexity.</p> <p>Because there weren't enough production-like workloads that showed significant gains (except perhaps SPECjBB), the option was removed.</p> <p>There is another angle to this. The option reduces heap usage. For applicable Strings, it reduces the memory usage of those Strings by 1/2. This angle wasn't considered at the time of option removal. For workloads that are memory <strong>capacity</strong> constrained (i.e. have to run with limited heap space and GC takes a lot of time), this option can prove useful.</p> <p>If enough memory <strong>capacity</strong> constrained production-like workloads can be found to justify the option's inclusion, then <em>maybe</em> the option will be brought back.</p> <p><strong>Edit 3/20/2013:</strong> An average server heap dump uses 25% of the space on Strings. Most Strings are compressible. If the option is reintroduced, it could save half of this space (e.g. ~12%)!</p> <p><strong>Edit 3/10/2016:</strong> A feature similar to compressed strings is coming back in JDK 9 <a href="http://openjdk.java.net/jeps/254" rel="noreferrer">JEP 254</a>.</p>
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    1. POSupport for Compressed Strings being Dropped in HotSpot JVM?
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    1. USNathan
    1. USNathan
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    1. POSupport for Compressed Strings being Dropped in HotSpot JVM?
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    1. COI assume that large JEE based systems will store most of their data in a database, JSE systems do this but to a lesser degree. Being able to store less data in memory reduces the size of the cache you can have but it is less critical (i.e. you won't get a failure as such) I am assuming the SPECjBB doesn't take into account the cost of being able to cache less data. For my applications, I store most of my data in Memory Mapped Files with byte based encoding for strings and use re-usable StringBuilder rather than String to limit GC impact, so it may not help me as much as it did.
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      1. USPeter Lawrey
    2. COIt shouldn't have to come at a price. Java should be able to provide apis that could be used to build a string from a source that is known to only contain bytes. Instead it chooses to distrust the programmer and verify everything itself. Similarly, java could provide an api allowing a String to be instantiated out of an existing array; instead it completely distrusts all programmers and forces always copying the array.
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      1. USsrparish
    3. COI hope this is added back in. It actually is very useful for speeding up text parsing applications that handle minimal character sets and definitely reduces heap usage if you're keeping your dataset in memory.
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      1. USJonathan S. Fisher
 

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