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POGet random value from HashMap
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  1. POGet random value from HashMap
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    copied!<p>I want to get random value of HashMap, but only from one key.</p> <p>This is how i build my HashMap. Every Key has multiple values.</p> <pre><code>ArrayList&lt;HashMap&lt;String, String&gt;&gt; items = new ArrayList&lt;HashMap&lt;String, String&gt;&gt;(); for (.....) { // creating new HashMap HashMap&lt;String, String&gt; map = new HashMap&lt;String, String&gt;(); Element e = (Element) nl.item(i); map.put(KEY_1, parser.getValue(e, KEY_1)); map.put(KEY_2, parser.getValue(e, KEY_2)); // adding HashList to ArrayList items.add(map); } </code></pre> <p>So key "KEY_1" has multiple values so do "KEY_2". Now i want to get random value using key "KEY_1". How to do that ?</p> <p>EDIT: I think i know where is problem, although dont know yet how to fix that. Problem is defining size(); I need somehow get size not from all HashMap items like "items.size();" but something more similar to "items.KEY_1.size();"</p> <p>With this code getting NullPointerException</p> <pre><code>int index = random.nextInt(items.size()); HashMap&lt;String, String&gt; randomitem = new HashMap&lt;String, String&gt;(); randomitem = items.get(index); System.out.println(randomitem.get(KEY_1)); </code></pre> <p>With this code im able to get value not random:</p> <pre><code>int index = 2; HashMap&lt;String, String&gt; randomitem = new HashMap&lt;String, String&gt;(); randomitem = items.get(index); System.out.println(randomitem.get(KEY_1)); </code></pre> <p><strong>EDIT:</strong> With this code i can get random values but i get values from all keys. How to get values only from one key ?</p> <pre><code>Random rand = new Random(); indexx = rand.nextInt(items.size()); System.out.println(items.get(indexx)); </code></pre> <p><strong>Solved</strong> With this code i can get random value from certain key.</p> <pre><code>Random rand = new Random(); indexx = rand.nextInt(items.size()); HashMap&lt;String, String&gt; randomitems = items.get(indexx); System.out.println(randomitems.get(KEY_1)); </code></pre>
 

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