You should use something like that :
IMethodBinding binding = node.resolveMethodBinding();
ITypeBinding typeBinding = expression.resolveTypeBinding();
ITypeBinding type = binding.getDeclaringClass();
Expression expression = node.getExpression();
System.out.println("Type: " + typeBinding.getName());
From the doc i have found many method that you want : http://help.eclipse.org/indigo/index.jsp?topic=%2Forg.eclipse.jdt.doc.isv%2Freference%2Fapi%2Forg%2Feclipse%2Fjdt%2Fcore%2Fdom%2FMethodInvocation.html
Try to check all method from varaible i have give you
Your question look similar to How to get a class name of a method by using Eclipse JDT ASTParser?