Alternative to MoreObjects in Java 8

Why not build the String yourself? The code is simple to write and to understand, without using any Java 8 specific features.

@Override
public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append(getClass().getSimpleName()).append('{')
    sb.append("userId=").append(userId);
    sb.append(", timestamp=").append(timestamp);
    return sb.append('}').toString();
}

I don't see any reason to use this toStringHelper even prior to Java 8. The plain implementation is not longer:

@Override
public String toString() {
    return getClass().getSimpleName()+"["
          +"userId: "+this.userId+", "
          +"timestamp: "+this.timestamp
          +"]";
}

You can use StringJoiner from java.util package.

Example:

@Override
public String toString() {
    return new StringJoiner(", ", ClassName.class.getSimpleName() + "[", "]")
    .add("userId=" + userId)
    .add("timestamp=" + timestamp)
    .toString();
}

Just featuring a pretty cool solution to let IntelliJ Idea generate the toString with StringJoiner: https://gist.github.com/vlastikcz/6a3b5c158bdb7bf6e9fd (thanks a lot to the author)
Add the code to toString templates: press Alt+Insert, select toString, then select Settings besides Templates, add with the Plus sign: