Minecraft plugin does not work because of a new PC?

Jo recently redesigned my PC and had to reload the Java version to program for my program.

Every time I export my Minecraft project there's a console error that gives me the following:

Could not load 'plugins \ KnockIt.jar' in folder 'plugins'

org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: de / veteran / main / main has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0

at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin (JavaPluginLoader.java:135) ~ [spigot.jar: git-Spigot-db6de12-18fbb24]

at org.bukkit.plugin.SimplePluginManager.loadPlugin (SimplePluginManager.java:329) ~ [spigot.jar: git-Spigot-db6de12-18fbb24]

at org.bukkit.plugin.SimplePluginManager.loadPlugins (SimplePluginManager.java:251) [spigot.jar: git-Spigot-db6de12-18fbb24]

at org.bukkit.craftbukkit.v1_8_R3.CraftServer.loadPlugins (CraftServer.java:292) [spigot.jar: git-Spigot-db6de12-18fbb24]

at org.bukkit.craftbukkit.v1_8_R3.CraftServer.reload (CraftServer.java:739) [spigot.jar: git-Spigot-db6de12-18fbb24]

at org.bukkit.Bukkit.reload (Bukkit.java:535) [spigot.jar: git-Spigot-db6de12-18fbb24]

at org.bukkit.command.defaults.ReloadCommand.execute (ReloadCommand.java:25) [spigot.jar: git-Spigot-db6de12-18fbb24]

at org.bukkit.command.SimpleCommandMap.dispatch (SimpleCommandMap.java:141) [spigot.jar: git-Spigot-db6de12-18fbb24]

at org.bukkit.craftbukkit.v1_8_R3.CraftServer.dispatchCommand (CraftServer.java:641) [spigot.jar: git-Spigot-db6de12-18fbb24]

at org.bukkit.craftbukkit.v1_8_R3.CraftServer.dispatchServerCommand (CraftServer.java:627) [spigot.jar: git-Spigot-db6de12-18fbb24]

at net.minecraft.server.v1_8_R3.DedicatedServer.aO (DedicatedServer.java:412) [spigot.jar: git-Spigot-db6de12-18fbb24]

at net.minecraft.server.v1_8_R3.DedicatedServer.B (DedicatedServer.java:375) [spigot.jar: git-Spigot-db6de12-18fbb24]

at net.minecraft.server.v1_8_R3.MinecraftServer.A (MinecraftServer.java:654) [spigot.jar: git-Spigot-db6de12-18fbb24]

at net.minecraft.server.v1_8_R3.MinecraftServer.run (MinecraftServer.java:557) [spigot.jar: git-Spigot-db6de12-18fbb24]

Could someone help me there or tell me which Java version I need to install?

Your plugin was compiled with Java 11 (version 55) but you only have Java 8 (version 52). Compile the plugin again with Java 8

What are you programming with? The program

You have to go to Java 11

IntelliJ, you know how I set it up there. A little while ago.