How to find how many times a method is used?

A general answer to this question would be something like this:

Static variable

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public class MyClass {
    static int count = 0;
    public void myMethod() {
        count++;
    }
}

Using static int would seem a perfect solution. Static will share the instance variable count among all instances of MyClass.
However, problem occurs in a multi threaded environment, as the count incrementation is not synchronised.

Multi-threaded

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package com.deepumohan.tech.methodinvocationcount;
public class MyClass {
    static int count = 0;
    public void myMethod() {
        synchronized(this) {
            count++;
        }
    }
}

Now this works perfect in a multi-threaded environment.

Thread safe atomic class

Java provides a better option to use thread-safe increments through Atomic classes available in java.util.concurrent.atomic packag.

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package com.deepumohan.tech.methodinvocationcount;
import java.util.concurrent.atomic.AtomicInteger;
public class MyClass {
    AtomicInteger atomicInteger = new AtomicInteger(0);
    public int getMethodInvocationCount() {
        return atomicInteger.incrementAndGet();
    }
}

Here is a good read about AtomicInteger vs static int: Java - using AtomicInteger vs Static int