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

I've made a plugin that sends a message to every player who join the server. I've been searching about this error, but I've not be able to fix it. When I run the server, it sends me this message:

Could not load 'plugins\JoiningGreetings.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: Cannot find main class `me.manujonex.JoininGreetings.Main.java'
at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:80) ~[spigot.jar:git-Spigot-dcd1643-e60fc34]
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:129) ~[spigot.jar:git-Spigot-dcd1643-e60fc34]
at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:327) ~[spigot.jar:git-Spigot-dcd1643-e60fc34]
at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:248) [spigot.jar:git-Spigot-dcd1643-e60fc34]
at org.bukkit.craftbukkit.v1_12_R1.CraftServer.loadPlugins(CraftServer.java:305) [spigot.jar:git-Spigot-dcd1643-e60fc34]
at net.minecraft.server.v1_12_R1.DedicatedServer.init(DedicatedServer.java:205) [spigot.jar:git-Spigot-dcd1643-e60fc34]
at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:545) [spigot.jar:git-Spigot-dcd1643-e60fc34]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_261]
Caused by: java.lang.ClassNotFoundException: me.manujonex.JoininGreetings.Main.java
at java.net.URLClassLoader.findClass(Unknown Source) ~[?:1.8.0_261]
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:152) ~[spigot.jar:git-Spigot-dcd1643-e60fc34]
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:100) ~[spigot.jar:git-Spigot-dcd1643-e60fc34]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_261]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_261]
at java.lang.Class.forName0(Native Method) ~[?:1.8.0_261]
at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_261]
at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:78) ~[spigot.jar:git-Spigot-dcd1643-e60fc34]

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