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POArrayList or several for loops?
 

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  1. POArrayList or several for loops?
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    <p>I know this might be simple, I have a situation where I need to decide between using four for-loops to (two to count and remove null elements, two to add elements) merge two String arrays or use two for-loops with an ArrayList and convert the ArrayList to array using ArrayList.toArray().</p> <p>Performance wise are there any differences between these two approaches?</p> <p>EDIT</p> <p>I had to drop the ArrayList with generics approach because of compatibility issues. But here is the earlier code.</p> <pre><code>List&lt;String&gt; newList = new ArrayList&lt;String&gt;(); for (String element : array1) { if (element != null) { newList.add(element); } } for (String element : array2) { if (element != null) { newList.add(element); } } return newList.toArray(new String[]{}); </code></pre> <p>I wrote a new code with one loop, but I think I might be mentally killing the next one reading this code. </p> <pre><code>String[] newArr = new String[array1.length + array2.length]; int n = 0; for (int i = 0; i &lt; newArr.length; i++) { if (i &lt; array1.length &amp;&amp; array1[i] != null) { newArr[n] = array1[i]; n++; } if (i &gt;= array1.length) { int a = 0; if (array1.length &lt; array2.length) { a = (i - array1.length) + (array2.length - array1.length); } else { a = i - array1.length; } if (array2[a] != null) { newArr[n] = array2[a]; n++; } } } return newArr; </code></pre> <p>And finally got to know that null element check won't be needed so went ahead with this simple code.</p> <pre><code>String[] newArr = new String[array1.length + array2.length]; System.arraycopy(array1, 0, newArr, 0, array1.length); System.arraycopy(array2, 0, newArr, array1.length, array2.length); return newArr; </code></pre> <p>I guess from the discussion below the second method is the better performing one. </p>
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    1. USChamila
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    1. COCan you paste your code ?
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      1. USꜱᴜʀᴇꜱʜ ᴀᴛᴛᴀ
    2. COYou might want to consider using LinkedList instead, unless you know the size of the array in beforehand.
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      1. USSimon Forsberg
    3. COIt probably depends. It usually does. So benchmark it, with exactly *your* realistic scenario, and compare. Btw, LinkedList is usually disappointingly slow.
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      1. USharold
 

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