[1.15.2] Game crashes when I try to test mod

[MrTheFool]

I am completely new to modding, I followed a setup video tutorial, but now I'm getting this...

Spoiler

 ---- Minecraft Crash Report ----
// Don't do that.

Time: 5/16/20 11:12 AM
Description: Initializing game

java.lang.NoSuchMethodError: java.nio.ByteBuffer.rewind()Ljava/nio/ByteBuffer;
    at net.minecraft.client.MainWindow.loadIcon(MainWindow.java:188) ~[forge-1.15.2-31.1.0_mapped_snapshot_20190719-1.14.3-recomp.jar:?] {re:classloading,pl:runtimedistcleaner:A}
    at net.minecraft.client.MainWindow.setWindowIcon(MainWindow.java:152) ~[forge-1.15.2-31.1.0_mapped_snapshot_20190719-1.14.3-recomp.jar:?] {re:classloading,pl:runtimedistcleaner:A}
    at net.minecraft.client.Minecraft.<init>(Minecraft.java:380) ~[forge-1.15.2-31.1.0_mapped_snapshot_20190719-1.14.3-recomp.jar:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
    at net.minecraft.client.main.Main.main(Main.java:141) ~[forge-1.15.2-31.1.0_mapped_snapshot_20190719-1.14.3-recomp.jar:?] {re:classloading,pl:runtimedistcleaner:A}
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_251] {}
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_251] {}
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_251] {}
    at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_251] {}
    at net.minecraftforge.userdev.FMLUserdevClientLaunchProvider.lambda$launchService$0(FMLUserdevClientLaunchProvider.java:55) ~[forge-1.15.2-31.1.0_mapped_snapshot_20190719-1.14.3-recomp.jar:?] {}
    at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37) [modlauncher-5.0.0-milestone.4.jar:?] {}
    at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:54) [modlauncher-5.0.0-milestone.4.jar:?] {}
    at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:72) [modlauncher-5.0.0-milestone.4.jar:?] {}
    at cpw.mods.modlauncher.Launcher.run(Launcher.java:81) [modlauncher-5.0.0-milestone.4.jar:?] {}
    at cpw.mods.modlauncher.Launcher.main(Launcher.java:65) [modlauncher-5.0.0-milestone.4.jar:?] {}
    at net.minecraftforge.userdev.LaunchTesting.main(LaunchTesting.java:102) [forge-1.15.2-31.1.0_mapped_snapshot_20190719-1.14.3-recomp.jar:?] {}

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Thread: Render thread
Stacktrace:
    at net.minecraft.client.MainWindow.loadIcon(MainWindow.java:188)
    at net.minecraft.client.MainWindow.setWindowIcon(MainWindow.java:152)
    at net.minecraft.client.Minecraft.<init>(Minecraft.java:380)

-- Initialization --
Details:
Stacktrace:
    at net.minecraft.client.main.Main.main(Main.java:141)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at net.minecraftforge.userdev.FMLUserdevClientLaunchProvider.lambda$launchService$0(FMLUserdevClientLaunchProvider.java:55)
    at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37)
    at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:54)
    at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:72)
    at cpw.mods.modlauncher.Launcher.run(Launcher.java:81)
    at cpw.mods.modlauncher.Launcher.main(Launcher.java:65)
    at net.minecraftforge.userdev.LaunchTesting.main(LaunchTesting.java:102)

-- System Details --
Details:
    Minecraft Version: 1.15.2
    Minecraft Version ID: 1.15.2
    Operating System: Windows 10 (amd64) version 10.0
    Java Version: 1.8.0_251, Oracle Corporation
    Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
    Memory: 603512048 bytes (575 MB) / 1743781888 bytes (1663 MB) up to 3786407936 bytes (3611 MB)
    CPUs: 12
    JVM Flags: 1 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump
    Launched Version: MOD_DEV
    Backend library: LWJGL version 3.2.2 build 10
    Backend API: GeForce GTX 1070/PCIe/SSE2 GL version 4.6.0 NVIDIA 419.72, NVIDIA Corporation
    GL Caps:
    Using VBOs: Yes
    Is Modded: Definitely; Client brand changed to 'forge'
    Type: Client (map_client.txt)
    CPU: <unknown>
[m[32m[11:12:51] [Render thread/INFO] [STDOUT/]: [net.minecraft.util.registry.Bootstrap:printToSYSOUT:109]: #@!@# Game crashed! Crash report saved to: #@!@# C:\Users\adam\OneDrive\Desktop\1.15.2 test mod\run\.\crash-reports\crash-2020-05-16_11.12.51-client.txt
[m

Where did I mess up?

[MrTheFool]

Excellent! It appears to be working now. Thanks for the help!

Edited May 16, 2020 by MrTheFool