strutsexample.java

@SuppressWarnings("unchecked")
protected void addError(String key, ActionErrors actionErrors, ActionError errorToAdd){
    if(StringUtils.isNotBlank(key) && actionErrors != null && errorToAdd != null){
        Iterator<ActionError> it = actionErrors.get(key);
        boolean okToAdd = true;
        //empty iterator returned where key not in action errors so no need for null check
        while(it.hasNext()){
            ActionError error = it.next();
            if(StringUtils.equals(error.getKey(), errorToAdd.getKey())){
                okToAdd = false;
            }
        }
        if(okToAdd){
            actionErrors.add(key, errorToAdd);
        }
    }
}