Sequential printing

test.java

import java.util.concurrent.locks.LockSupport;

public class test {

    public static void main(String[] args) {
        final Thread t6 = new Thread(new T(6, null));
        final Thread t5 = new Thread(new T(5, t6));
        final Thread t4 = new Thread(new T(4, t5));
        final Thread t3 = new Thread(new T(3, t4));
        final Thread t2 = new Thread(new T(2, t3));
        final Thread t1 = new Thread(new T(1, t2));

        t1.start();
        t2.start();
        t3.start();
        t4.start();
        t5.start();
        t6.start();

    }

    @RequiredArgsConstructor
    public static class T implements Runnable {

        private final int i;
        private final Thread next;

        public void print() {
            System.out.println(i);
            if (next != null) {
                LockSupport.unpark(next);
            }
        }

        public T park() {
            LockSupport.park();
            return this;
        }

        public void run() {
            if (this.i == 1) {
                this.print();
            } else {
                park();
                this.print();
            }
        }
    }
}