logback-android/src/main/java/ch/qos/logback/core/OutputStreamAppender.java
public void start() {
    int errors = 0;
    if (this.encoder == null) {
      addStatus(new ErrorStatus("No encoder set for the appender named \""
          + name + "\".", this));
      errors++;
    }

    if (this.outputStream == null) {
      addStatus(new ErrorStatus(
          "No output stream set for the appender named \"" + name + "\".", this));
      errors++;
    }
    // only error free appenders should be activated
    if (errors == 0) {
      super.start();
    }
  }
public void start() {
    int errors = 0;
    if (this.encoder == null) {
      addStatus(new ErrorStatus("No encoder set for the appender named \""
          + name + "\".", this));
      errors++;
    }

    if (this.outputStream == null) {
      addStatus(new ErrorStatus(
          "No output stream set for the appender named \"" + name + "\".", this));
      errors++;
    }
    // only error free appenders should be activated
    if (errors == 0) {
      super.start();
    }
  }
Checks that requires parameters are set and if everything is in order,
activates this appender.