Error Loading Minecraft in Eclipse

Hello there I was making a mod and I tried to launch Minecraft Forge in Eclipse and this happened:
[15:47] [main/INFO] [GradleStart]: No arguments specified, assuming client.
[15:47] [main/INFO] [GradleStart]: Extra: []
[15:47] [main/INFO] [GradleStart]: Running with arguments: [--userProperties, {}, --assetsDir, C:/Users/Edward.ENEVARD-DESKTOP/.gradle/caches/minecraft/assets, --assetIndex, 1.7.10, --accessToken, {REDACTED}, --version, 1.7.10, --tweakClass, cpw.mods.fml.common.launcher.FMLTweaker, --username, ForgeDevName]
[15:47] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLTweaker
[15:47] [main/INFO] [LaunchWrapper]: Using primary tweak class name cpw.mods.fml.common.launcher.FMLTweaker
[15:47] [main/INFO] [LaunchWrapper]: Calling tweak class cpw.mods.fml.common.launcher.FMLTweaker
[15:47] [main/INFO] [FML]: Forge Mod Loader version 7.10.25.1207 for Minecraft 1.7.10 loading
[15:47] [main/INFO] [FML]: Java is Java HotSpot(TM) 64-Bit Server VM, version 1.8.0_20, running on Windows 8.1:amd64:6.3, installed at C:\Program Files\Java\jdk1.8.0_20\jre
[15:47] [main/INFO] [FML]: Managed to load a deobfuscated Minecraft name- we are in a deobfuscated environment. Skipping runtime deobfuscation
[15:47] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
[15:47] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLDeobfTweaker
[15:47] [main/INFO] [LaunchWrapper]: Calling tweak class cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
[15:47] [main/ERROR] [LaunchWrapper]: Unable to launch
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901) ~[?:1.8.0_20]
at java.util.ArrayList$Itr.remove(ArrayList.java:865) ~[?:1.8.0_20]
at net.minecraft.launchwrapper.Launch.launch(Launch.java:117) [launchwrapper-1.9.jar:?]
at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.9.jar:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_20]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_20]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_20]
at java.lang.reflect.Method.invoke(Method.java:483) ~[?:1.8.0_20]
at GradleStart.bounce(GradleStart.java:107) [start/:?]
at GradleStart.startClient(GradleStart.java:100) [start/:?]
at GradleStart.main(GradleStart.java:55) [start/:?]
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
at GradleStart.main(GradleStart.java:59)
Java HotSpot(TM) 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release
It didn't open, I am new to java coding and have no clue what this means... PLEASE HELP
-Edned