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    <p>I would approach this problem by identifying what is needed. You have a list of categories (Strings). Within each category, there will be a list of question (String) and answer (String) pairs. From there we already see some "logical" ways to organize the data.</p> <ul> <li>Questions - String</li> <li>Answers - String</li> <li>Question/Answer pairs - Write a class (for now, lets refer to it as QAPair) with two Strings as fields (one for the question, one for the answer)</li> <li>List of Q/A pairs within a category - ArrayList</li> <li>List of Categories, mapped to a list of Q/A pairs - Maybe a <a href="http://docs.oracle.com/javase/7/docs/api/java/util/Map.html" rel="nofollow">Map</a> would do the trick. The type would be: Map></li> </ul> <p>From there you would start parsing the file; for the first line, or after a blank line is encountered, you know the String will give a category name. You can call containsKey() to check if the category name already exists; if it does fetch the ArrayList of Q/A Pairs for that category and keep adding to the list, otherwise initialize a new ArrayList and add it to the map for that category.</p> <p>You could then read a pair of lines. For each pair of lines you read initialize a QAPair object, then add it to the ArrayList for the category they belong to.</p> <p>Here's an example of using a Map:</p> <pre><code>Map&lt;String, ArrayList&lt;QAPair&gt;&gt; categories = new HashMap&lt;String, ArrayList&lt;QAPair&gt;&gt;(); if (!categories.containsKey("Math")) { // Check to see if a Math category exists categories.put("Math", new ArrayList&lt;QAPair&gt;()); // If it doesn't, create it } QAPair question1 = new QAPair("2+2", "4"); // get() method returns the ArrayList for the "Math" category // add() method adds the QAPair to the ArrayList for the "Math" category categories.get("Math").add(question1); </code></pre> <p>To get the list of categories from a map and pick one:</p> <pre><code>// Convert to an array of Strings String[] catArray = categories.toArray(new String[0]); // Get the 10th category in the array // Use catArray.length to find how many categories there are total catArray[10]; </code></pre>
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    1. POFormat an arraylist
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    1. USRyan
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    1. COExcept you can't initialise `Map` as it is an interface
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      1. USJava Devil
    2. COFair point. Let's say it's a HashMap. TreeMap or LinkedHashMap could also work.
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