Java regex replacing all the characters except few combination of characters
<p>Input String : <code>NNULL(EUR,VALUE)+SOMESTR</code></p>

<p>Expected output:<code>NNULL(X,X)+X</code></p>

<p>Expression tried: </p>

<pre><code>String str = "NNULL(EUR,VALUE)+SOMESTR";
str=str.replaceAll("[^(NNULL)\\+,]+","X");
</code></pre>

<p>Output getting: </p>

<pre><code>NNULL(XUX,XLUX)+X
</code></pre>