public class ExtendedLanguage extends GCCLanguage implements ICLanguageKeywords{
	
	@Override
	public String[] getKeywords() {
		//System.out.println("Called keywords" + timesKey++);
		return new String[]{
				"hello",
				"printme"
		};
	}

	@Override
	public String[] getBuiltinTypes() {
	//	System.out.println("Called keywords" + timesBuilt++);
		return new String[]{
				"Lambros",
				"Petrou"
		};
	}
	
	@Override
	public String[] getPreprocessorKeywords() {
		//System.out.println("Called keywords" + timesPre++);
		return new String[]{
				"pre1",
				"pre2"
		};
	}

	 @Override
     public String getId() {
         return "ExtendedC";
     }

	@SuppressWarnings("rawtypes")
	public Object getAdapter(Class adapter) {
		if (ICLanguageKeywords.class.equals(adapter)) 
			return this;
		return super.getAdapter(adapter);
    }
}

<extension
		id="extendedlanguage1.ExtendedCExtension"
       point="org.eclipse.cdt.core.language">
         <language
         	class="extendedlanguage1.ExtendedLanguage"
         	id="ExtendedC"
         	name="Extended C Language">
           <contentType id="org.eclipse.cdt.core.cSource"/>
           <contentType id="org.eclipse.cdt.core.cHeader"/>
      </language>
   </extension>