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POHow to Sort 2D ArrayList<String> by Only the First Element
 

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  1. POHow to Sort 2D ArrayList<String> by Only the First Element
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    <p><strong>To avoid the duplicate claims</strong>, I've looked at <a href="https://stackoverflow.com/questions/1512366/java-2d-arraylist-and-sorting">this</a> post and it isn't exactly what I wanted. <br> Every other 2D ArrayList question involved <code>double</code> or <code>int</code> numbers; my question is about <code>Strings</code>. </p> <h3>What I'm doing</h3> <p>I have a 2D ArrayList, defined like this:</p> <pre class="lang-java prettyprint-override"><code>ArrayList&lt;ArrayList&lt;String&gt;&gt; namesAndNumbers = new ArrayList&lt;ArrayList&lt;String&gt;&gt;(); </code></pre> <p>The idea is that the first item in every row of ArrayLists contains the names, and the rest of the columns in each row contains the phone numbers (unknown amount). Therefore I would like to avoid converting it to a regular array.</p> <h3>Sample</h3> <p>Let's say I've populated my ArrayList and I have this:</p> <pre class="lang-java prettyprint-override"><code>{"Mike", "(805) 766-4920"} {"Emily", "(705) 668-9292", "(705) 555-1060"} {"James", "(605) 965-2000"} </code></pre> <p>I expect my <strong>output</strong> to be this:</p> <pre class="lang-java prettyprint-override"><code>{"Emily", "(705) 668-9292", "(705) 555-1060"} {"James", "(605) 965-2000"} {"Mike", "(805) 766-4920"} </code></pre> <p>I want to keep the numbers corresponding with the names, but simply sort the array by the name.</p> <h3>What answers I hope for </h3> <p>I'm hoping for a built-in function manipulation type of thing, but I'd be fine if someone created a sorting array method for me with an 2D ArrayList as the input. I haven't seen any question that answers this issue explicitly. <em>I will continue trying to come up with an answer myself as well</em>.</p>
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    1. USMichael Yaworski
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    1. COWhy don't you use Collections in Java for this - i think that would be a perfect tool for your case, isn't it?
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    2. CO@harikris it is a nested ArrayList. Yes, I think Collections can work but I have no idea what to do with it.
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      1. USMichael Yaworski
    3. COIf you used Collections, then sorting would become a breeze. Also, instead of Lists, if you used Sets, then you can avoid duplicate entries as well - all done automatically for you. It's not difficult to learn about Collections and Generics. May i suggest a reference book? Not sure if that will come across as promotional. I did not write this book. Just think it's an excellent resource. Authors are Kathy Sierra and Bert Bates. They have a chapter on Collections/Generics in their Head First Java book. HTH.
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