Memory Analyzer WeakHashMap

Memory Analyzer WeakHashMap

save Heap dump using jconsole :

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\Users\vikas.verma1>cd workspace\demo

C:\Users\vikas.verma1\workspace\demo>
C:\Users\vikas.verma1\workspace\demo>cd src

C:\Users\vikas.verma1\workspace\demo\src>jmap -dump:format=b,file=heap.bin 6016
Dumping heap to C:\Users\vikas.verma1\workspace\demo\src\heap.bin ...
Heap dump file created

C:\Users\vikas.verma1\workspace\demo\src>

---------------------------------

Here I am tried with Integer value in weakHashMap key is an large object as Employee.
debug.memory: allocated: 1,362.00MB of 3,616.00MB (1,204.00MB free)

Here Now with same object for value and key.

https://www.toptal.com/java/hunting-memory-leaks-in-java#memleak

https://developers.redhat.com/blog/2014/08/14/find-fix-memory-leaks-java-application/

package com.gc.refrences;

import static com.jayway.awaitility.Awaitility.await;

import java.lang.ref.WeakReference;
import java.text.DecimalFormat;
import java.util.HashMap;
import java.util.WeakHashMap;
import java.util.concurrent.TimeUnit;

class Employee1 {
	private String name;
	private int id;
	private Object object;

	public Employee1(String name, int id) {
		super();
		this.name = name;
		this.id = id;
		object = largeObj();
	}

	public void setName(String name) {
		this.name = name;
	}

	public Object largeObj() {
		StringBuilder stringB = new StringBuilder(2000000); // for the 2mb one
		String paddingString = getName();

		while (stringB.length() + paddingString.length() < 2000000)
			stringB.append(paddingString);

		// use it
		return stringB.toString();
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public int getId() {
		return id;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + id;
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Employee1 other = (Employee1) obj;
		if (id != other.id)
			return false;
		if (name == null) {
			if (other.name != null)
				return false;
		} else if (!name.equals(other.name))
			return false;
		return true;
	}
}

public class MemoryAnayzer {
	public static void main(String[] args) {

		// Blo
		logHeap();
		//HashMap<Employee, Employee> hm = new HashMap<>();
		//WeakHashMap<Employee1, WeakReference<Employee1>> hm = new WeakHashMap();
		WeakHashMap<Employee1, Integer> hm = new WeakHashMap();

		for (int i = 0; i < 500; i++) {
			Employee1 e1 = new Employee1("vikas" + i, i);
			Employee1 e2 = new Employee1("Ram" + i, 501 + i);
			
			WeakReference<Employee1> reference = new WeakReference(e1);
			WeakReference<Employee1> reference1 = new WeakReference(e2);
			hm.put(e1, i);
			hm.put(e2, 501+i);
		}
		
		//System.gc();
		logHeap();
		
	}

	public static void logHeap() {
		DecimalFormat df = new DecimalFormat();
		df.setMaximumFractionDigits(2);
		df.setMinimumFractionDigits(2);

		System.out.println("debug. =================================");
		System.out.println(
				"debug.memory: allocated: " + df.format(new Double(Runtime.getRuntime().totalMemory() / 1048576))
						+ "MB of " + df.format(new Double(Runtime.getRuntime().maxMemory() / 1048576)) + "MB ("
						+ df.format(new Double(Runtime.getRuntime().freeMemory() / 1048576)) + "MB free)");
	}

}
o/p ::debug.memory: allocated: 1,306.00MB of 3,616.00MB (1,023.00MB free)


Here Now with same object for value and key: