Java 8 - 使用JsonObject（javax.json） - 如何确定节点是否有子节点？

I've just started using javax.json package. I know how to extract values from JSON object in Java 8 if I know the structure of my JSON string. But how about strings I don't know the structure of? The question: how to determine if a node has child nodes?I've just started using javax.json package. I k