Java JRE and SDK Support and Performance

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JRE/SDK	Works	Compiles	Performance
Oracle/Sun? 5	no	no	I2P 0.9.12 and newer requires Java 1.6 or newer
Oracle/Sun? 6	yes	yes	good
Oracle/Sun? 7	yes	yes	good
GCJ (compiled to C)	no	no	very poor
GCJ-JRE (gij-4.4)	no	I2P 0.9.12 and newer requires Java 1.6 or newer
Iced Tea 5	no	no	I2P 0.9.12 and newer requires Java 1.6 or newer
Iced Tea 6	yes	yes (no on PPC "1.6.0_18" OpenJDK Runtime Environment (IcedTea6 1.8) - missing Pack200 - see ​http://forum.i2p/viewtopic.php?t=4655 ) - see note below	good
Iced Tea 7	yes	yes	good
Open JDK 5	no	no	I2P 0.9.12 and newer requires Java 1.6 or newer
Open JDK 6	yes	yes	good, except on ARM systems such as the Raspberry Pi. Use Oracle Java 7 or 8 on these platforms.
Open JDK 7	yes	yes	good, except on ARM systems such as the Raspberry Pi. Use Oracle Java 7 or 8 on these platforms.
Open JDK 8	yes	yes	good, except on ARM systems such as the Raspberry Pi. Use Oracle Java 7 or 8 on these platforms.
IBM	Reportedly does not ​http://zzz.i2p/topics/577
Android	yes	yes (core and router)	poor/OK depending on hardware; 512 MB RAM recommended
Oracle/BEA JRockit 1.6	yes	yes	good
Apache Harmony 5	no - bug in Deflater fixed with workaround in 0.7.12-15; reports huge clock skews in UDP Transport; works with TCP only?		slow
Apache Harmony 6
JamVM 1.5.3	yes	n/a	poor
CacaoVM/openjdk6	wrapper hangs at jvm launch	yes	fail

NOTES:

<smeghead> icedtea is openjdk with the non-GPL-compatible parts replaced, and openjdk is sun's jdk with bits relicensed

<smeghead> for most purposes you shouldn't notice any difference between sun, openjdk, and icedtea

<smeghead> however, icedtea offers some alternatives to hotspot which can give worse or better performance

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As of I2P 0.9.12, a 1.6 compatible SDK is required to compile I2P. A 1.6 or higher JRE is required to run I2P.