I have confronted problem of moving Flex 3 code to flex 4 code with the following comipling problem:
"unbound classpath container: 'jre system library [flex builder 3]' in project"
Man Pak Hong, Dave
oops ! i find the solution: Right-click the project -> properties -> java build path -> click the JRE System library -> choose alternate JRE to Adobe Flash Builder 4
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