What is the right lambda for this inner class.SonarLint suggest me to "Make this anonymous inner class a lambda"

Question

return new KeyGenerator() {
    @Override
    public Object generate(Object object, Method method, Object... objects) {
    String username = null;
    try {
        username = objectStorageService.getAuthDetail().getUsername();
        StringBuilder customisedkey = generateKey(object, method, objects);
        customisedkey.append(username);
        return customisedkey.toString();
    } catch (BaseException e) {
       LOGGER.error("Operation failed while generating Key", e);
       return null;
    }
}
};

SonarLint suggest me to "Make this anonymous inner class a lambda". but wasn't able to find a solution for this specific case

Answer 1

An anonymous inner class having just a single method can be converted in a lambda expression.

In particular this code:

return new KeyGenerator() {
    @Override
    public Object generate(Object object, Method method, Object... objects) {
    String username = null;
    try {
        username = objectStorageService.getAuthDetail().getUsername();
        StringBuilder customisedkey = generateKey(object, method, objects);
        customisedkey.append(username);
        return customisedkey.toString();
    } catch (BaseException e) {
       LOGGER.error("Operation failed while generating Key", e);
       return null;
    }
}
};

is equivalent to:

return (object, method, objects) -> {
    String username = null;
    try {
        username = objectStorageService.getAuthDetail().getUsername();
        StringBuilder customisedkey = generateKey(object, method, objects);
        customisedkey.append(username);
        return customisedkey.toString();
    } catch (BaseException e) {
       LOGGER.error("Operation failed while generating Key", e);
       return null;
    }
};

More in general a code similar to this one:

new MyClass() {
   public ReturnType myUniqueMethod(ParameterType p) {
       // body
   }
}

can be replaced with

(p) -> {
   // body
}

This operation can be generally executed automatically by modern IDE with a refactoring operation.