core/play/src/main/java/play/mvc/Controller.java
@Deprecated
  public static void flash(String key, String value) {
    flash().put(key, value);
  }
@Deprecated
  public static void flash(String key, String value) {
    flash().put(key, value);
  }
Puts a new value into the flash scope.

@param key the key to put into the flash scope
@param value the value corresponding to <code>key</code>
@deprecated Deprecated as of 2.7.0. Use {@link Result} instead.