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POcode to prove that hashMap is fail-Safe
 

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  1. POcode to prove that hashMap is fail-Safe
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    <p>Question Edited :<br> HashSet and HashMap are fail-fast(but that is not gauranteed) as mentioned in code :</p> <pre><code>void goHashSet() { Set set = new HashSet(); for (int i = 1; i &lt;= 10; i++) { set.add(i); } Iterator i = set.iterator(); while (i.hasNext()) { // set.add(16);//Exception in thread "main" // java.util.ConcurrentModificationException System.out.println("HashSet &gt;&gt;&gt; itertor &gt;&gt;&gt;" + i.next()); } } </code></pre> <p>Now, i want the example and the collections which are fail-safe<br> as much as i know: ConcurrentHashMap,CopyOnWriteArrayList are fail-safe..but how to code it to show that they are fail-safe</p> <p><strong>Edit and Undestanding of what I want and how I achieved it :</strong></p> <p>if we use HashMap</p> <pre><code>void goHashMap() { Map mp = new HashMap(); for (int i = 19; i &lt;= 24; i++) { mp.put(i, "x"); } Set setKeys = mp.keySet(); Iterator i = setKeys.iterator(); while (i.hasNext()) { // mp.put(499, "x");// Exception in thread "main" // java.util.ConcurrentModificationException System.out.println("HashMap &gt;&gt;&gt; itertor &gt;&gt;&gt;" + i.next()); } } </code></pre> <p>we get ConcurrentMException</p> <p>but the same code is done with ConcurrentHashMap, no error is there (non-multithreading enviro)</p> <pre><code>void goConcurrentHashMap() { Map mp = new ConcurrentHashMap(); for (int i = 19; i &lt;= 24; i++) { mp.put(i, "x"); } Set setKeys = mp.keySet(); Iterator i = setKeys.iterator(); while (i.hasNext()) { mp.put(499, "x"); System.out.println("HashConcurrentMap &gt;&gt;&gt; itertor &gt;&gt;&gt;" + i.next()); } } </code></pre> <p>whats more : in multithreading enviro the ConcurrentHashmap might get fail-fast and throw exception CME</p>
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    1. CO*"I understand what is fail-safe/fast is"* - based, on your question, I'm not sure that you do ... really.
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      1. USStephen C
    2. CO@StephenC hmm,you might be right...but i have edited the question altogether...and whole purpose of the question is to see an example of fail-fast in code
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