Steps to Reproduce:
1. Download the Apache SDK using AIR tool (available at http://people.apache.org/~bigosmallm/installapacheflex/ ) which also packages the SDK to use with Flash builder.
2. Download JRE 1.7
3. Install Flash Builder 4.6
4. Go to the installed FB location and delete the JRE folder already present in the FB installed location
5. Copy the JRE 1.7 folder into the installed location. (jre folder should be renamed from jre7 to jre)
FB will now use JRE 1.7 instead of using the bundled 1.6
6. Configure FB to use Apache SDK which was downloaded in step 1.
7. Create a Flex project using Apache SDK
8. Now create a new AS class inside the new project
Actual result: Internal build error in problems view. The error log says that there was an uncaught exception in the compiler.
Expected result: There should be no such errors
Workaround: Add a line "-Djava.util.Arrays.useLegacyMergeSort=true" in the FlashBuilder.ini
Note: This issue is specific to Apache SDK. It is working fine with the released version of Flex SDK 4.6