How to Measure the Size of Objects in Java?

Measuring Object Size in Java

In Java, determining the memory consumption of an object is not as straightforward as in languages like C/C where the sizeof() function can be utilized. However, an alternative approach exists using the java.lang.instrumentation package.

This package provides a versatile method for obtaining an implementation-specific approximation of an object's size, including any associated overhead:

<code class="java">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);
    }
}</code>

To use this functionality, simply call getObjectSize() like so:

<code class="java">public class C {
    private int x;
    private int y;

    public static void main(String[] args) {
        System.out.println(ObjectSizeFetcher.getObjectSize(new C()));
    }
}</code>

This approach offers a robust way to estimate the memory consumption of Java objects, enabling developers to analyze and optimize data structures effectively.

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