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To install Groovy 2.0, go to Help --> Install new Software. In the work with tab, choose the Groovy-Eclipse update site and select the Extra Compilers category:

Read Compiler Switching within Groovy-Eclipse for more information on how to install Groovy 2.0 and how to switch compiler levels.
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There is now a project setting that records the last compiler level that compiled it. You can access this setting in the Groovy Compiler settings page for the project:

This is in addition to the workspace compiler level, which is found at Preferences -> Groovy -> Compiler:

If the compiler level for the project is different from that of the workspace, then an error marker is placed on the project and it cannot be built until the compiler levels are resolved:

To resolve the marker discrepancy,
select the marker or markers that you want to fix, and you can choose one of three ways to resolve the conflict:

You can choose to:
- Configure the compiler level for the project(s), which opens a dialog where you can manually choose a compiler level
- Change the compiler level for the entire workspace (i.e., change which compiler is being used in the workspace). This requires a restart.
- Or simply set the project compiler level to match the workspace compiler level. Most of the time, this is the option you will want to choose.
Better Content assist for Annotation
Content assist in the context of an annotation, will only show annotations, not classes, interfaces, or enums:

Compatibility
Groovy-Eclipse 2.7.1 uses Groovy 1.8.6. Groovy 1.7.10 can be enabled optionally, and Groovy 2.0.4 can be installed through the extra compilers section on the update site.
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