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);
    }
  }
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