Calculate size of Object in Java
You can use the java.lang.instrumentation
package.
It has a method that can be used to get the implementation specific approximation of object size, as well as overhead associated with the object.
The answer that Sergey linked has a great example, which I'll repost here, but you should have already looked at from his comment:
import java.lang.instrument.Instrumentation;
public class ObjectSizeFetcher {
private static Instrumentation instrumentation;
public static void premain(String args, Instrumentation inst) {
instrumentation = inst;
}
public static long getObjectSize(Object o) {
return instrumentation.getObjectSize(o);
}
}
Use getObjectSize
:
public class C {
private int x;
private int y;
public static void main(String [] args) {
System.out.println(ObjectSizeFetcher.getObjectSize(new C()));
}
}
Source
Look into https://github.com/DimitrisAndreou/memory-measurer.
Guava uses it internally, and ObjectGraphMeasurer
is especially straightforward to use out-of-the-box, without any special command-line arguments.
import objectexplorer.ObjectGraphMeasurer;
public class Measurer {
public static void main(String[] args) {
Set<Integer> hashset = new HashSet<Integer>();
Random random = new Random();
int n = 10000;
for (int i = 1; i <= n; i++) {
hashset.add(random.nextInt());
}
System.out.println(ObjectGraphMeasurer.measure(hashset));
}
}