题解 | #表达式求值#，哈哈，想起来了大佬的骚操作

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) throws ScriptException {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNext()) { // 注意 while 处理多个 case
            String next = in.next();
            ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
            ScriptEngine nashorn = scriptEngineManager.getEngineByName("nashorn");
            System.out.println(nashorn.eval(next));
        }
    }
}