java.security.MessageDigest

MessageDigestを使えば簡単にJavaでMD5やSHA1でのハッシュ値を算出できる

import java.security.MessageDigest;

public class Sample {
    public static void main(String[] args) throws Exception {
        MessageDigest md = MessageDigest.getInstance("MD5");
        md.update("1234".getBytes());
        byte[] b = md.digest();

        for(int i = 0; i < b.length; i++) {
            int v = b[i] < 0 ? b[i] + 256 : b[i];
            String s = v < 16 ? "0" + Integer.toString(v, 16) : Integer.toString(v, 16);
            System.out.print(s);
        }
    }
}