FOUND THE SOLUTION
public void getHashMapFromArrayList(ArrayList list,
String variableName){
HashMap resultMap=new HashMap();
try{
for(int i=0;i<list.size();i++){
Object obj=list.get(i);
Class listClass=obj.getClass();
Class[] paramTypes = null;
Method method = listClass.getMethod(variableName, paramTypes);
int valueId=new Integer(method.invoke(obj,paramTypes).toString()).intValue();
System.err.println("obj.instance"+valueId);
resultMap.put(valueId+"",obj);
}
}catch(Exception e){
e.printStackTrace();
}
}