DecimalFormat nf = new DecimalFormat("0000");
System.out.println(nf.format(1254));
System.out.println(nf.format(12546));
System.out.println(nf.format(10));
System.out.println(nf.format(1254));
System.out.println(nf.format(12546));
System.out.println(nf.format(10));
s = "0000" + s;
s = s.substring(s.length()-4);
System.out.println(s); //0010