SimpleSemaphore.java

class SimpleSemaphore {
    private int S;

    public SimpleSemaphore(int initialPermits) {
        this.S = initialPermits;
    }

    public synchronized void acquire() throws InterruptedException {
        while (S <= 0) {
            wait(); // Block until a permit is available
        }
        S--;
    }

    public synchronized void release() {
        S++;
        notify(); // Wake up a waiting thread
    }
}