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POJava pattern for parameters of which only one needs to be non-null?
 

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  1. POJava pattern for parameters of which only one needs to be non-null?
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    <p>In the last time I often write long functions that have several parameters but use only one of them and the functionality is only different at a few keypoints that are scattered around the function. Thus splitting the function would create too many small functions without a purpose. Is this good style or is there a good general refactoring pattern for this? To be more clear, an example:</p> <pre><code>public performSearch(DataBase dataBase, List&lt;List&lt;String&gt;&gt; segments) {performSearch(dataBase,null,null,segments);} public performSearch(DataBaseCache dataBaseCache,List&lt;List&lt;String&gt;&gt; segments) {performSearch(null,dataBaseCache,null,segments);} public performSearch(DataBase dataBase, List&lt;String&gt; keywords {performSearch(dataBase,null,keywords,null);} public performSearch(DataBaseCache dataBaseCache,List&lt;String&gt; keywords) {performSearch(null,dataBaseCache,keywords,null);} /** either dataBase or dataBaseCache may be null, dataBaseCache is used if it is non-null, else dataBase is used (slower). */ private void performSearch(DataBase dataBase, DataBaseCache dataBaseCache, List&lt;String&gt; keywords, List&lt;List&lt;String&gt;&gt; segments) { SearchObject search = new SearchObject(); search.setFast(true); ... search.setNumberOfResults(25); if(dataBaseCache!=null) {search.setSource(dataBaseCache);} else {search.setSource(dataBase);} ... do some stuff ... if(segments==null) { // create segments from keywords .... segments = ... } } </code></pre> <p>This style of code works but I don't like all those null parameters and the possibilities of calling methods like this wrong (both parameters null, what happens if both are non-null) but I don't want to write 4 seperate functions either... I know this may be too general but maybe someone has a general solution to this principle of problems :-)</p> <p>P.S.: I don't like to split up a long function if there is no reason for it other than it being long (i.e. if the subfunctions are only ever called in that order and only by this one function) especially if they are tightly interwoven and would need a big amount of parameters transported around them.</p>
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    1. USKonrad Höffner
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      1. VTUpMod
    1. COIntroduce [parameter object](http://www.refactoring.com/catalog/introduceParameterObject.html).
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      1. USJordão
    2. COHm but as far as I understand the link, a parameter object is for different parameters that are used together, not alternatively. I mean my 2 parameter objects would only need to hold one object at a time, just that the class is different.
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      1. USKonrad Höffner
    3. COwhat type does `search.setSource(` accept? is it a parent type common to `DataBase` and `DataBaseCache`.
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      1. USbasiljames
 

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