Created
July 23, 2011 13:07
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example that shows the difference in the strategy used to implement the string pool in JVMs. watch for the effect of PermGen removal in newer HotSpot
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| $ use6u25 | |
| $ java -version | |
| java version "1.6.0_25" | |
| Java(TM) SE Runtime Environment (build 1.6.0_25-b06) | |
| Java HotSpot(TM) 64-Bit Server VM (build 20.0-b11, mixed mode) | |
| $ groovysh | |
| Groovy Shell (1.7.5, JVM: 1.6.0_25) | |
| Type 'help' or '\h' for help. | |
| ------------------------------------------------------------------------------- | |
| groovy:000> s = new String([(byte) 'a', (byte) 'b'] as byte[]) | |
| ===> ab | |
| groovy:000> t = s.intern() | |
| ===> ab | |
| groovy:000> s.is t | |
| ===> false | |
| groovy:000> quit | |
| $ use7b144 | |
| $ java -version | |
| java version "1.7.0-ea" | |
| Java(TM) SE Runtime Environment (build 1.7.0-ea-b144) | |
| Java HotSpot(TM) 64-Bit Server VM (build 21.0-b14, mixed mode) | |
| $ groovysh | |
| Groovy Shell (1.7.5, JVM: 1.7.0-ea) | |
| Type 'help' or '\h' for help. | |
| ------------------------------------------------------------------------------- | |
| groovy:000> s = new String([(byte) 'a', (byte) 'b'] as byte[]) | |
| ===> ab | |
| groovy:000> t = s.intern() | |
| ===> ab | |
| groovy:000> s.is t | |
| ===> true | |
| groovy:000> quit | |
| $ usejrockit | |
| $ java -version | |
| java version "1.6.0_20" | |
| Java(TM) SE Runtime Environment (build 1.6.0_20-b02) | |
| Oracle JRockit(R) (build R28.0.1-21-133393-1.6.0_20-20100512-2126-linux-x86_64, compiled mode) | |
| rednaxelafx@fx-laptop:~/build$ groovysh | |
| Groovy Shell (1.7.5, JVM: 1.6.0_20) | |
| Type 'help' or '\h' for help. | |
| ------------------------------------------------------------------------------- | |
| groovy:000> s = new String([(byte) 'a', (byte) 'b'] as byte[]) | |
| ===> ab | |
| groovy:000> t = s.intern() | |
| ===> ab | |
| groovy:000> s.is t | |
| ===> true | |
| groovy:000> quit | |
| $ usej9 | |
| $ java -version | |
| java version "1.6.0" | |
| Java(TM) SE Runtime Environment (build pxa6460sr8fp1-20100624_01(SR8 FP1)) | |
| IBM J9 VM (build 2.4, JRE 1.6.0 IBM J9 2.4 Linux amd64-64 jvmxa6460sr8ifx-20100609_59383 (JIT enabled, AOT enabled) | |
| J9VM - 20100609_059383 | |
| JIT - r9_20100401_15339ifx2 | |
| GC - 20100308_AA) | |
| JCL - 20100624_01 | |
| $ groovysh | |
| Groovy Shell (1.7.5, JVM: 1.6.0) | |
| Type 'help' or '\h' for help. | |
| ------------------------------------------------------------------------------- | |
| groovy:000> s = new String([(byte) 'a', (byte) 'b'] as byte[]) | |
| ===> ab | |
| groovy:000> t = s.intern() | |
| ===> ab | |
| groovy:000> s.is t | |
| ===> false | |
| groovy:000> quit |
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