32-Bit VS 64-Bit JVM


How To Choose 32-Bit or 64-Bit JVM
http://www.techpaste.com/2012/02/choose-32-bit-64-bit-jvm/

Default JVM settings GC, JIT and Java Heap Sizes -Xms & -Xmx on different operating systems
http://www.techpaste.com/2012/02/default-jvm-settings-gc-jit-java-heap-sizes-xms-xmx-operating-systems/

Is a JVM's Maximum Heap Size really 1.7 GB?
http://pauldone.blogspot.tw/2008/08/is-jvms-maximum-heap-size-really-17-gb.html

REF:
java - Benefits/drawbacks to running 64-bit JVM on 64-bit Linux server? - Stack Overflow
http://stackoverflow.com/questions/559433/benefits-drawbacks-to-running-64-bit-jvm-on-64-bit-linux-server

WAS 7之後支援compressed reference

http://www.ibm.com/developerworks/cn/websphere/library/techarticles/0809_alcott/0809_alcott.html

WebSphere Application Server V7 中的新特性

IBM 的 Java SE 6 中的另一个改进是在 64 位 WebSphere Application Server JVM 中使用
压缩引用 (compressed reference)(或指针压缩)。与以前的 32 位 JVM 相比,使用压缩引用可以非常显著地减少 64 位 JVM 的进程内存占用空间。在 IBM 推出 Java SE 6 实现以前,64 位堆的大小为等效的 32 位堆的 1.7 至 2 倍的情况并不鲜见。


IBM JVM:
 -Xcompressedrefs

Oracle JVM:
-XX:+UseCompressedOops

Use -Xcompressedrefs in any of these situations:

  • When your Java applications does not need more than a 25 GB Java heap.
  • When your application uses a lot of native memory and needs the JVM to run in a small footprint.

REF:
http://publib.boulder.ibm.com/infocenter/javasdk/v6r0/index.jsp?topic=%2Fcom.ibm.java.doc.diagnostics.60%2Fdiag%2Funderstanding%2Fmm_compressed_references.html

http://www.slideserve.com/adamdaniel/improving-64-bit-java-performance-using-compressed-references

MongoDB綁定伺服器IP

./mongod --bind_ip 127.0.0.1

MongoDB 授權

AGPL v3.0
http://www.gnu.org/licenses/agpl-3.0.html

授權流言終結者#4:MongoDB 授權的分析與探討(雙重授權模式 2.0) - OpenFoundry
http://www.openfoundry.org/tw/enterprise-application/8687-4mongodb-20

2012年6月21日 星期四

State Diagram的狀態移轉

http://www.developer.com/design/article.php/2238131/State-Diagram-in-UML.htm

Transition: An arrow indicating the Object to transition from one state to the other. The actual trigger event and action causing the transition are written beside the arrow, separated by a slash. Transitions that occur because the state completed an activity are called "triggerless" transitions.

事件產生後且條件滿足 => 執行Action讓狀態移轉

2012年6月20日 星期三

2012年6月13日 星期三

else if有return值就變成if

剛剛發現else if有return值編譯器好像會自動改成if
如果沒有return值decompile還是else if
試了兩個版本的Sun JDK都一樣