为了解决另一个常见的复杂问题，也就是从System.in 读取内容和通过System.out.println打印内容的问题，JEP 512 引入了一个工具类java.lang.IO。

System. out. println (s. length ()); } The difference is clear: No redundant casting: The variable s is ready to use as a String. Cleaner logic: Combines type-checking and assignment in one line.

Execute System.out.println($1) and you’ll see 52 as the output. You can run jshell with the -v command-line argument (jshell -v) to generate verbose feedback.