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POJava - Swapping Page
 

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    <p>I have built a custom hashmap using two arrays. One contains keys another values. Now, I see sometimes JVM can't able to allocate required memory for those arrays and throws exception. Is there any method to solve this using page swapping or any other method ?</p> <p>Code:</p> <pre><code>public class Test1{ public static void main(String args[]){ try { int arrays[] = new int[50000000] ; for ( int i = 0; i &lt; 50000000 ; i++) { arrays[i] = i ; } } catch(Exception e){ System.out.println(e) ; } } } </code></pre> <p>Edit:</p> <pre><code> public void load() { try { FileChannel channel2 = new RandomAccessFile(str1, "r").getChannel(); MappedByteBuffer mbb2 = channel2.map(FileChannel.MapMode.READ_ONLY, 0, channel2.size()); mbb2.order(ByteOrder.nativeOrder()); assert mbb2.remaining() == savenum * 8; for (int i = 0; i &lt; savenum; i++) { long l = mbb2.getLong(); keys[i] = l; } channel2.close(); FileChannel channel3 = new RandomAccessFile(str2, "r").getChannel(); MappedByteBuffer mbb3 = channel3.map(FileChannel.MapMode.READ_ONLY, 0, channel3.size()); mbb3.order(ByteOrder.nativeOrder()); assert mbb3.remaining() == savenum * 4; for (int i = 0; i &lt; savenum; i++) { int l1 = mbb3.getInt(); values[i] = l1; } channel3.close(); } catch (Exception e) { System.out.println(e); } } public void save() { try { FileChannel channel = new RandomAccessFile(str1, "rw").getChannel(); MappedByteBuffer mbb = channel.map(FileChannel.MapMode.READ_WRITE, 0, savenum * 8); mbb.order(ByteOrder.nativeOrder()); for (int i = 0; i &lt; savenum; i++) { mbb.putLong(keys[i]); } channel.close(); FileChannel channel1 = new RandomAccessFile(str2, "rw").getChannel(); MappedByteBuffer mbb1 = channel1.map(FileChannel.MapMode.READ_WRITE, 0, savenum * 4); mbb1.order(ByteOrder.nativeOrder()); for (int i = 0; i &lt; savenum; i++) { mbb1.putInt(values[i]); } channel1.close(); } catch (Exception e) { System.out.println("IOException : " + e); } } </code></pre>
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    1. COTry starting the JVM with more heap space?
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    2. CODid you consider a SQL database?
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    3. COPage swapping is something the operating system does. Make sure you don't have any actual memory leaks first. (As a first step, profile the memory use of the application with a huge maximum heap size and check if it settles at some point.)
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