How to parse a Hashmap in java 1.4

How to parse a Hashmap in java 1.4

Hi i'm working with java 1.4 and iwant to implement this :
// protected HashMap droppedFileTarget;
JExpression[] params = new JExpression[2];
for (String extension : droppedFileTarget.keySet()) {
String field = droppedFileTarget.get(extension);
params[1]=VKUtils.toExpression(ref, extension);
params[2]=VKUtils.toExpression(ref, field);
}
but i'm getting this compilation error :
type mismatch : can not convert from Object to String
Even after type cast but the error persists :
for (String extension : (String) droppedFileTarget.keySet())