Question

I have a java form in which i have declared different variables of type string , and few variables of type string array and few are collections.
Using getdeclaredfileds of reflection api , i am getting every field of class in my field array variable.
But i want to separate the string variables into one common array.
array strings into other array and collection fields into other one.

eg: – String abc;
String def;
String[] lmn;
String[] opq;
Collection mno;

Answer 1

Define a utility method:

public static Map<Class<?>, List<Field>> getFieldsByType(Field[] fields) {
  Map<Class<?>, List<Field>> result = new HashMap<Class<?>, List<Field>>();
  for (Field field:fields) {
    List<Field> fieldList = result.get(field.getType());
    if (fieldList == null) {
      fieldList = new ArrayList<Field>();
      result.put(field.getType(), fieldList);
    }
    fieldList.add(field);
  }
  return result;
}

It separates the fields by type and stores them in a map.

Example usage:

Map<Class<?>, List<Field>> map = getFieldsByType(MyClass.class.getDeclaredFields());
List<Field> stringTypeMembers = map.get(String.class);

Now stringTypeMember contains all class members (fields) that are of type String.