package finalizerdemo;

import java.io.*;

public class C implements Closeable
{
    private int index;
    private C other;
    private boolean closed = false;

    public C(int index)
    {
        this.index = index;
    }

    public void setOther(C other)
    {
        this.other = other;
    }

    @Override
    public void close() throws IOException
    {
        if(!closed)
        {
            closed = true;
            finalizerAssert(other != null); // the other object must be still available
            finalizerAssert(index + 1 == other.index || index - 1 == other.index);  // the two indexes must be exactly 1 from each other
            System.out.print(" other(" + other.index + ")");
            if(index > other.index)
            {
                System.out.println(" calling other#close");
                System.out.print("\t");
                other.close();
            }
            other = null;   // just to make sure if we did something wrong, we would get an assertion error
        }
    }

    @Override
    protected void finalize() throws Throwable
    {
        System.out.print("C(" + index + ")#finalize");
        close();
        System.out.println(" finalizer finished");
    }

    private static void finalizerAssert(boolean success)
    {
        if(!success)
        {
            new AssertionError().printStackTrace();
            System.exit(1);
        }
    }

    public static void main(String[] args)
    {
        for(int i = 0; true; i += 2)
        {
            C a = new C(i);
            C b = new C(i + 1);
            a.setOther(b);
            b.setOther(a);
            System.out.print('.');  // this is just an indicator that GC doesn't run after every iteration
        }
    }
}