StringUtilities.java :  » Music » harmonium » net » roarsoftware » util » Java Open Source

package net.roarsoftware.util;

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.HashMap;
import java.util.Map;
import java.util.regex.Pattern;

/**
 * Utilitiy class with methods to calculate an md5 hash and to encode URLs.
 *
 * @author Janni Kovacs
 */
public class StringUtilities {

  private static MessageDigest digest;
  private static Pattern MBID_PATTERN = Pattern
      .compile("^[0-9a-f]{8}\\-[0-9a-f]{4}\\-[0-9a-f]{4}\\-[0-9a-f]{4}\\-[0-9a-f]{12}$",
          Pattern.CASE_INSENSITIVE);
  private static final Pattern MD5_PATTERN = Pattern.compile("[a-zA-Z0-9]{32}");

  static {
    try {
      digest = MessageDigest.getInstance("MD5");
    } catch (NoSuchAlgorithmException e) {
      // better never happens
    }
  }

  public static String md5(String s) {
    try {
      byte[] bytes = digest.digest(s.getBytes("UTF-8"));
      StringBuilder b = new StringBuilder(32);
      for (byte aByte : bytes) {
        String hex = Integer.toHexString((int) aByte & 0xFF);
        if (hex.length() == 1)
          b.append('0');
        b.append(hex);
      }
      return b.toString();
    } catch (UnsupportedEncodingException e) {
      // utf-8 always available
    }
    return null;
  }

  public static String encode(String s) {
    try {
      return URLEncoder.encode(s, "UTF-8");
    } catch (UnsupportedEncodingException e) {
      // utf-8 always available
    }
    return null;
  }

  public static String decode(String s) {
    try {
      return URLDecoder.decode(s, "UTF-8");
    } catch (UnsupportedEncodingException e) {
      // utf-8 always available
    }
    return null;
  }

  public static boolean isMbid(String artistOrMbid) {
    // example: bfcc6d75-a6a5-4bc6-8282-47aec8531818
    return artistOrMbid.length() == 36 && MBID_PATTERN.matcher(artistOrMbid).matches();
  }

  /**
   * Creates a Map out of an array with Strings.
   *
   * @param strings input strings, key-value alternating
   * @return a parameter map
   */
  public static Map<String, String> map(String... strings) {
    if (strings.length % 2 != 0)
      throw new IllegalArgumentException("strings.length % 2 != 0");
    Map<String, String> mp = new HashMap<String, String>();
    for (int i = 0; i < strings.length; i += 2) {
      mp.put(strings[i], strings[i + 1]);
    }
    return mp;
  }

  /**
   * Strips all characters from a String, that might be invalid to be used in file names.
   * By default <tt>: / \ < > | ? " *</tt> are all replaced by <tt>-</tt>.
   * Note that this is no guarantee that the returned name will be definately valid.
   *
   * @param s the String to clean up
   * @return the cleaned up String
   */
  public static String cleanUp(String s) {
    return s.replaceAll("[*:/\\\\?|<>\"]", "-");
  }

  /**
   * Tests if the given string might already be a 32-char md5 string.
   *
   * @param s String to test
   * @return <code>true</code> if the given String might be a md5 string
   */
  public static boolean isMD5(String s) {
    return s.length() == 32 && MD5_PATTERN.matcher(s).matches();
  }
}