code: static public void configureCfRenaming(Configuration conf, 
            Map<String, String> renameMap) {
      StringBuilder sb = new StringBuilder();
      for(Map.Entry<String,String> entry: renameMap.entrySet()) {
        String sourceCf = entry.getKey();
        String destCf = entry.getValue();
  
        if(sourceCf.contains(":") || sourceCf.contains(",") || 
                destCf.contains(":") || destCf.contains(",")) {
          throw new IllegalArgumentException("Illegal character in CF names: " 
                + sourceCf + ", " + destCf);
        }
  
        if(sb.length() != 0) {
          sb.append(",");
        }
        sb.append(sourceCf + ":" + destCf);
      }
      conf.set(CF_RENAME_PROP, sb.toString());
    }
docs: <p>Sets a configuration property with key {@link #CF_RENAME_PROP} in conf that tells
  the mapper how to rename column families.
  
  <p>Alternately, instead of calling this function, you could set the configuration key
  {@link #CF_RENAME_PROP} yourself. The value should look like
  <pre>srcCf1:destCf1,srcCf2:destCf2,....</pre>. This would have the same effect on
  the mapper behavior.
  
  @param conf the Configuration in which the {@link #CF_RENAME_PROP} key will be
  set
  @param renameMap a mapping from source CF names to destination CF names