package com.alibaba.druid.stat;
import java.lang.management.ManagementFactory;
import java.text.NumberFormat;
import java.util.HashMap;
import java.util.Map;
import junit.framework.TestCase;
public class HashMapMemoryTest extends TestCase {
public void test_0() throws Exception {
HashMap item = new HashMap();
gc();
long memoryStart = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getUsed();
final int COUNT = 1024 * 1024;
Map[] items = new Map[COUNT];
for (int i = 0; i < COUNT; ++i) {
items[i] = new HashMap();
// items[i] = Histogram.makeHistogram(20);
}
long memoryEnd = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getUsed();
System.out.println("memory used : " + NumberFormat.getInstance().format(memoryEnd - memoryStart));
}
private void gc() {
for (int i = 0; i < 10; ++i) {
System.gc();
}
}
}