In this directory, you will find Eclipse projects for many of the
projects.  They are divided into two groups: The "java" directory
contains Eclipse JDT projects for the Java-based parts of the Flex
SDK, such as the compiler and the debugger, and the "flex" directory
has Flex Builder projects for the Flex-based parts of the SDK, such
as the Flex framework. To use them:

(1) In the preferences, in both General > Workspace > Linked Resources
    and Java > Build Path > Classpath Variables, set FLEX_SDK to point
    to the root directory of your SDK.

(2) Import using File > Import, Existing Projects into Workspace.