Thread: java compilation error

i am unable to compile this code on redhat linux

package hiveudf;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.Text;
public class lowercaseudf extends UDF {
    public Text evaluate(final Text s) {
        if (s == null) { return null;}
        return new Text(s.toString().lowerCase());
        }
        }
}

# javac -classpath /usr/hdp/2.6.5.0-292/hive2/lib/*:/usr/hdp/2.6.5.0-292/hadoop/*:/usr/hdp/2.6.5.0-292/hadoop-mapreduce/* lowercaseudf.java
lowercaseudf.java:7: error: cannot find symbol
        return new Text(s.toString().lowerCase());
                                    ^
  symbol:   method lowerCase()
  location: class String
1 error