logback-android/src/main/java/ch/qos/logback/core/FileAppender.java
public void setFile(String file) {
    if (file == null) {
      fileName = null;
    } else {
      // Trim spaces from both ends. The users probably does not want
      // trailing spaces in file names.
      fileName = file.trim();
    }
  }
public void setFile(String file) {
    if (file == null) {
      fileName = null;
    } else {
      // Trim spaces from both ends. The users probably does not want
      // trailing spaces in file names.
      fileName = file.trim();
    }
  }
The <b>File</b> property takes a string value which should be the name of
the file to append to.
@param file path to destination log file