logback-android/src/main/java/ch/qos/logback/core/property/FileExistsPropertyDefiner.java
public String getPropertyValue() {
    if (OptionHelper.isEmpty(path)) {
      addError("The \"path\" property must be set.");
      return null;
    }

    File file = new File(path);
    return booleanAsStr(file.exists());
  }
public String getPropertyValue() {
    if (OptionHelper.isEmpty(path)) {
      addError("The \"path\" property must be set.");
      return null;
    }

    File file = new File(path);
    return booleanAsStr(file.exists());
  }
Returns "true" if the file specified by {@link #setPath(String) path} property exists.
Returns "false" otherwise.

@return "true"|"false" depending on the existence of file