Last login: Mon Jul 26 11:07:56 on ttys000
GjydeMacBook-Air:~ gjy$ /Users/gjy/Desktop/456/start.command ; exit;
Exception in thread "main" java.lang.UnsupportedClassVersionError: net/minecraft/server/MinecraftServer : Unsupported major.minor version 52.0
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClassCond(ClassLoader.java:637)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
        at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
logout
Saving session...
...copying shared history...
...saving history...truncating history files...
...completed.

（你的Java版本是多少？
首先更新到Java11
1.16.5等高版本需要改用Java16