ASTParser dependencies

I'm trying to learn ASTParser with the help of this tutorial. When I compile the first slice of code:

ASTParser parser = ASTParser.newParser(AST.JLS2); parser.setSource("".toCharArray()); CompilationUnit unit = (CompilationUnit) parser.createAST(null); unit.recordModifications()开发者_如何学C; AST ast = unit.getAST();

I get this error:

Source non found. The JAR of this class file belongs to container 'Plug-in Dependencies' which does not allow modifications to source attachments on its entries.

What can I do?

According to this, you should include these jar files:

• org.eclipse.core.contenttype.jar
• org.eclipse.core.jobs.jar
• org.eclipse.core.resources.jar
• org.eclipse.core.runtime.jar
• org.eclipse.equinox.common.jar
• org.eclipse.equinox.preferences.jar
• org.eclipse.jdt.core.jar
• org.eclipse.osgi.jar