logback-android/src/main/java/ch/qos/logback/core/util/OptionHelper.java
public static String substVars(String input, PropertyContainer pc0, PropertyContainer pc1) {
    try {
      return NodeToStringTransformer.substituteVariable(input, pc0, pc1);
    } catch (ScanException e) {
      throw new IllegalArgumentException("Failed to parse input [" + input + "]", e);
    }
  }
public static String substVars(String input, PropertyContainer pc0, PropertyContainer pc1) {
    try {
      return NodeToStringTransformer.substituteVariable(input, pc0, pc1);
    } catch (ScanException e) {
      throw new IllegalArgumentException("Failed to parse input [" + input + "]", e);
    }
  }
public static String substVars ( String input , PropertyContainer pc0 , PropertyContainer pc1 ) { try { return NodeToStringTransformer . substituteVariable ( input , pc0 , pc1 ) ; } catch ( ScanException e ) { throw new IllegalArgumentException ( "Failed to parse input [" + input + "]" , e ) ; } }
See  http://logback.qos.ch/manual/configuration.html#variableSubstitution
@param input string to be evaluated
@param pc0 primary property container
@param pc1 secondary property container
@return the substituted string
See http : // logback . qos . ch / manual / configuration . html#variableSubstitution