Question

I was trying to change a generic Map

private final Map<String, Object> dataObject;

to

private final Map<String, ?> dataObject;

The getter changes from

public Map<String, Object> getDataObject() {
  return dataObject;
}

to

public Map<String, ?> getDataObject() {
  return dataObject;
}

but the setter:

public void addDataObject(final String key, final Object value) {
  dataObject.put(key, value);
}

can’t be configured without error any idea? or am I doing wrong trying to use the “?” generic

Answer 1

Parameterize your class instead of using a wildcard:

class Container<T> {
  private final Map<String, T> dataObject;

  public Map<String, T> getDataObject() {
    return dataObject;
  }

  public void addDataObject(final String key, final T value) {
    dataObject.put(key, value);
  }

}