Java で md5 コマンドを作る

import java.security.MessageDigest;
import java.io.FileInputStream;

public class md5 {
    public static void main(String a[]) {
	try {
	    MessageDigest md = MessageDigest.getInstance("MD5");
	    for(int i=0; i<a.length; i++) {
		FileInputStream in = new FileInputStream(a[i]);
		byte[] dat = new byte[256];
		while(true) {
		    int len = in.read(dat);
		    if(len < 0) break;
		    md.update(dat, 0, len);
		}
		in.close();
		byte[] ddata = md.digest();
		System.out.print("MD5 (" + a[i] + ") = ");
		for(int j=0; j<ddata.length; j++) {
		    int r = (ddata[j] >= 0) ? ddata[j]:(256+ddata[j]);
		    if(r < 0x10) {
			System.out.print("0");
		    }
		    System.out.print(Integer.toString(r, 16));
		}
		System.out.println();
	    }
	} catch (Exception e) {
	    e.printStackTrace();
	}
    }
}