properties - read a property from another property(multiple levels) in java -

my situation this

i having property file

url.dev.a=devlocalhost   url.qa.a=qalocalhost   env=dev totalurl=${url.${env}.a} 

here expecting totalurl devlocalhost

how can in property file.

the following class cleaned open source project work with. if can't used is, can atleast starting point exploration.

package snippet;  import java.util.enumeration; import java.util.properties; import java.util.regex.matcher; import java.util.regex.pattern;  public class propertyreplace {      /**      * replaces java properties in properties of form %&lt;java      * property&gt; java property value.      *       * @param properties      *            , properties replacement takes place      */     public static void replaceenviron(properties properties) {         enumeration<object> enumeration = properties.keys();         while (enumeration.hasmoreelements()) {             string key = (string) enumeration.nextelement();             string value = properties.getproperty(key);             system.out.println("finding value key " + key);             string updatedvalue = getupdatedvalue(value, properties);             if (updatedvalue == null)                 updatedvalue = "";             properties.setproperty(key, updatedvalue);         }     }      /**      * value given mpf property.      *       * @param value      *            , original value      * @param properties      *            , properties replacements taken      * @return modified value      */     private static string getupdatedvalue(string value, properties properties) {         system.out.println("value = " + value);         if (value == null)             return null;         pattern p = pattern.compile("[^%]*(%[^%]*%).*");         matcher m = p.matcher(value);         while (m.matches()) {             string var = m.group(1);             string varvalue = getupdatedvalue(properties.getproperty(var.substring(1, var.length() - 1)), properties);             if (varvalue == null) {                 varvalue = system.getproperty(var.substring(1, var.length() - 1), null);                 if (varvalue == null) {                     varvalue = system.getenv(var.substring(1, var.length() - 1));                     if (varvalue == null)                         varvalue = "";                 }             }             value = value.replaceall(var, varvalue);             m = p.matcher(value);         }         system.out.println("return: " + value);         return value;     }      public static void main(string[] args) {         properties props = new properties();         // url.dev.a=devlocalhost         // url.qa.a=qalocalhost         // env=dev         // totalurl=${url.${env}.a}          props.setproperty("url.dev.a", "devlocalhost");         props.setproperty("url.qa.a", "qalocalhost");         props.setproperty("env", "dev");         props.setproperty("totalurlx", "url.%env%.a");         props.setproperty("totalurl", "%totalurlx%");          replaceenviron(props);          system.out.println(props);      }  }