public class Letter implements Runnable{
    public char[] ch = new char[26] ;

    public Letter() {
        for (int i = 0 ; i <ch.length ; i++) {
            ch[i] = (char) ('a'+i);
        }
    }


    @Override
    public void run() {
        for (int i = 0 ; i<ch.length ; i++){
            System.out.print(ch[i]);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.getMessage();
            }
        }
    }
}

​class Test {
    public static void main(String[] args) {
Letter L = new Letter();
Thread td = new Thread(L);
td.start();
    }

}