Encode/decode parameters in a format that is suitable to be sent as the encoded query string to Yahoo services with a HTTP API

YahooURI.java

package stackoverflow;

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

public class YahooURI {
  
  public static void main(String[] args) throws Exception {
    Multimap p = new Multimap();
    p.put("foo", "bar");
    p.remove("foo", "404");
    
    p.put("bar", "A string with spaces");
    p.put("baz", "àèìòù");
    p.put("qoo", "a b c");
    p.put("qoo", "A string, with comma");
    p.put("qoo", "à");
    p.remove("qoo", "a b c");
    
    String serialized = encode(p);
    System.out.println(serialized);
    
    p = decode(serialized);
    System.out.println(p);
  }
  
  static String encode(Multimap data) throws UnsupportedEncodingException {
    StringBuilder str = new StringBuilder();
    String delim = "";
    for (Entry<String, Set<String>> params : data) {
      str.append(delim);
      str.append(URLEncoder.encode(params.getKey(), "UTF8"));
      str.append("=");
      String delim2 = "";
      for (String value : params.getValue()) {
        // I think this is the only way to pass a literal comma
        str.append(delim2).append(URLEncoder.encode(value, "UTF8").replace(",", "%2C"));
        delim2 = ",";
      }
      delim = "&";
    }
    return str.toString();
  }
  
  static Multimap decode(String src) throws UnsupportedEncodingException {
    Multimap result = new Multimap();
    for (String token : src.split("&")) {
      String[] pair = token.split("=");
      String key = URLDecoder.decode(pair[0], "UTF8");
      for (String value : pair[1].split(",")) {
        result.put(key, URLDecoder.decode(value, "UTF8"));
      }
    }
    return result;
  }
  
  static class Multimap implements Iterable<Entry<String, Set<String>>>{
    
    Map<String, Set<String>> data = new LinkedHashMap<>();
    
    public Set<String> get(String key) {
      return data.get(key);
    }
    
    public void put(String key, String value) {
      Set<String> set = get(key);
      if (set == null) {
        set = new HashSet<>();
        data.put(key, set);
      }
      set.add(value);
    }
    
    public void remove(String key, String value) {
      Set<String> set = get(key);
      if (set != null) {
        set.remove(value);
        if (set.isEmpty()) {
          data.remove(key);
        }
      }
    }
    
    @Override
    public Iterator<Entry<String, Set<String>>> iterator() {
      return data.entrySet().iterator();
    }
    
    @Override
    public String toString() {
      StringBuilder str = new StringBuilder();
      String delim = "";
      for (Entry<String, Set<String>> entry : data.entrySet()) {
        for (String value : entry.getValue()) {
          str.append(delim);
          str.append(entry.getKey()).append(" -> ").append(value);
          delim = "\n";
        }
      }
      return str.toString();
    }
  }

}