having the same object as return type and input argument for a method in Java

Question

public static void prepareOutput (Output[]  parOutput, Input inputObj) 
{
    int arraySize  = parOutput.length;
    Output[] output = new Output[arraySize];
    for(int i=0; i<arraySize; i++)
    {           
        if(parOutput != null && parOutput[i].getSubscriptionsX7() != null)
        {
            output[i] = new Output();
            output[i] = setLevel1OutputObj(parOutput[i],inputObj, output[i]);
            output[i] = setLevel2OutputObj(parOutput[i],inputObj, output[i]);
            output[i] = setLevel3OutputObj(parOutput[i],inputObj, output[i]);
            output[i] = setLevel4OutputObj(parOutput[i],inputObj, output[i]);
        }   
    }
    inputObj.setSubscriberInfoOutput(output);
}

I have main Input object o1 which consists of object o2 . Object o2 consists of object o3 . Object o3 consists of object o4 .

Here I am passing the same output object in the argument and have it as return type as well. Can it be coded better?

Answer 1

输入inputObj使其成为类成员，因此您的方法仅将parOutput作为参数。

Answer 2

One option is to write a utility/helper function, like so:

public static Output configuredOutput(Output source, Input input) {
    if (source.getSubscriptionsX7() == null) {
        return null;
    }

    Output result = new Output();
    result = setLevel1OutputObj(source, input, result);
    result = setLevel2OutputObj(source, input, result);
    result = setLevel3OutputObj(source, input, result);
    result = setLevel4OutputObj(source, input, result);

    return result;
}

...and then implement your loop-body in the calling code like:

if(parOutput != null && parOutput[i].getSubscriptionsX7() != null) {
    output[i] = configuredOutput(parOutput[i],inputObj);
}   

Another option, and what I think you're actually asking about, is to implement method-chaining . To do that you'd have to refactor your setLevelXOutputObj functions to be instance methods on the Output class.

If you did so, you'd then be able to rewrite your loop-body with something like:

Output source = parOutput[i];
output[i] = new Output().setLevel1OutputObj(source, inputObj)
                        .setLevel2OutputObj(source, inputObj)
                        .setLevel3OutputObj(source, inputObj)
                        .setLevel4OutputObj(source, inputObj);

The fact that you're always passing the Object that you're working with as the final argument to your static functions is a good indication that your static functions would be more appropriately implemented as instance methods.

Note that as pbabcdefp states, you likely also want to look at your parOutput != null check. You don't really have it in a reasonable place, as your current code will throw a NullPointerException if parOutput is ever actually null .