Thread - Sleep and interrupt

Question

Please first see this snippet:

public static void main(String[] args) throws InterruptedException {
    Thread anotherThread = new Thread(() -> {
        Integer countB = 0;
        while (true) {
            try {
                System.out.println("B count: " + ++countB);
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    });
    anotherThread.start();

    Integer countA = 0;
    while (true) {
        System.out.println("A count: " + ++countA);
        Thread.sleep(1000);
    }
}

This works as expected. I see countA to be approximately 2x of countB.

Now I add one line to the outer while loop:

public static void main(String[] args) throws InterruptedException {
    Thread anotherThread = new Thread(() -> {
        Integer countB = 0;
        while (true) {
            try {
                System.out.println("B count: " + ++countB);
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    });
    anotherThread.start();

    Integer countA = 0;
    while (true) {
        anotherThread.interrupt();
        System.out.println("A count: " + ++countA);
        Thread.sleep(1000);
    }
}

Main thread interrupts anotherThread. After I do this, countA is no longer 2x countB. They always differ by one now.

Why so? How does sleep/interrupt work?

Answer 1

This is an addition to Buddy's answer, which is correct.

In first case you have

B    A
.    .
.    A
.    .
B    A
.    .
.    A
.    .
B    A

but with interrupt it changed to:

B    A (interrupts B, B continues in loop)
B    .
.    A (interrupts B again)
B    .
.    A
B    .
.    A
B    .
.    A

causing B not to wait 2 seconds...