Clones a map and prefixes the keys in the clone : Customized Map « Collections « Java Tutorial

1. Java Tutorial
2. Collections
3. Customized Map

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;


public class Main {


  /**
   * Clones a map and prefixes the keys in the clone, e.g.
   * for mapping "JAVA_HOME" to "env.JAVA_HOME" to simulate
   * the behaviour of ANT.
   *
   * @param source the source map
   * @param prefix the prefix used for all names
   * @return the clone of the source map
   */
  public static Map prefix(Map source, String prefix) {

      if(source == null) {
          return null;
      }

      Map result = new HashMap();

      Iterator iter = source.entrySet().iterator();

      while(iter.hasNext()) {
          Map.Entry entry = (Map.Entry) iter.next();
          Object key = entry.getKey();
          Object value = entry.getValue();
          result.put(prefix + '.' + key.toString(), value);
      }

      return result;
  }

}