/*******************************************************************************
* Copyright (c) 2002-2006 Innoopract Informationssysteme GmbH.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Innoopract Informationssysteme GmbH - initial API and implementation
******************************************************************************/
package com.w4t.ajax;
public class MemSize {
public static void main( final String[] args ) throws Exception {
// Warm up all classes/methods we will use
runGC();
usedMemory();
// Array to keep strong references to allocated objects
final int count = 100000;
Object[] objects = new Object[ count ];
long heap1 = 0;
// Allocate count+1 objects, discard the first one
for( int i = -1; i < count; ++i ) {
Object object = null;
// Instantiate your data here and assign it to object
object = new Object();
// object = new Integer (i);
// object = new Long (i);
// object = new String ();
// object = new byte [128][1]
if( i >= 0 )
objects[ i ] = object;
else {
object = null; // Discard the warm up object
runGC();
heap1 = usedMemory(); // Take a before heap snapshot
}
}
runGC();
long heap2 = usedMemory(); // Take an after heap snapshot:
final int size = Math.round( ( ( float )( heap2 - heap1 ) ) / count );
System.out.println( "'before' heap: " + heap1 + ", 'after' heap: " + heap2 );
System.out.println( "heap delta: "
+ ( heap2 - heap1 )
+ ", {"
+ objects[ 0 ].getClass()
+ "} size = "
+ size
+ " bytes" );
for( int i = 0; i < count; ++i ) {
objects[ i ] = null;
}
objects = null;
}
public static void runGC() throws Exception {
// It helps to call Runtime.gc()
// using several method calls:
for( int r = 0; r < 4; ++r ) {
_runGC();
}
}
private static void _runGC() throws Exception {
long usedMem1 = usedMemory(), usedMem2 = Long.MAX_VALUE;
for( int i = 0; ( usedMem1 < usedMem2 ) && ( i < 500 ); ++i ) {
Runtime.getRuntime().runFinalization();
Runtime.getRuntime().gc();
Thread.yield();
usedMem2 = usedMem1;
usedMem1 = usedMemory();
}
}
public static long usedMemory() {
Runtime runtime = Runtime.getRuntime();
return Runtime.getRuntime().totalMemory() - runtime.freeMemory();
}
}