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    <p>With the recursive method you would put one of your looping in a function pass the loop parameters to that function. Then from within the function's loop, it calls its to nest another loop.</p> <pre><code>void loopFunction(ArrayList&lt;ArrayList&lt;String&gt;&gt; newWords, int level) { if (level == 0) { // terminating condition if (/* compare the indices by for example passing down a list with them in */) { newWords.get(...).add(...); } } else {// inductive condition for (int i = 0; i &lt; len; i++) { loopFunction(newWords, level-1); } } } </code></pre> <p>So for your example you need 3 levels of recursion so you would start the recursion with:</p> <pre><code>loopFunction(newWords, 3); </code></pre> <p><strong>Edit</strong></p> <p>Since you have been having trouble here is a working version. It keeps a list of indices to compare against and it builds up the string as it goes. The rearranged words are added to the 2D array at each level to get all lengths of words. With recursion it is easiest to think functionally and not change and keep the variables immutable (unchangeable). This code mostly does that although I update the <code>indices</code> rather than create a new copy for convenience.</p> <pre><code>void loopFunction(ArrayList&lt;String&gt; lets, ArrayList&lt;ArrayList&lt;String&gt;&gt; newWords, int level, ArrayList&lt;Integer&gt; indices, String word) { if (level == 0) { // terminating condition return; } else { // inductive condition for (int i = 0; i &lt; lets.size(); i++) { if (!indices.contains(i)) { // Make sure no index is equal int nextLevel = level-1; String nextWord = word+lets.get(i); newWords.get(level-1).add(nextWord); indices.add(i); loopFunction(lets, newWords, nextLevel, indices, nextWord); indices.remove((Integer) i); } } } } </code></pre>
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    1. COif (i != j && i != k && j != k) this seems to be wrong.There are no j and k local variables in loopFunction()
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    2. COWoops got a bit copy/paste happy. Also would this benefit for tail recursion optimisations (for Java 8) or should it go down one more level?
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    3. COYou wrote the code `newWords.get(...).add(...);` In the add() part, I would need to have a collection of the letters. I don't know how to collect all the letters though. Can anyone help me with that?
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