java.lang.IndexOutOfBoundsException: Index: 5, Size: 5

Question

I am having an issue with arrays. The full stack trace is:

java.lang.IndexOutOfBoundsException: Index: 5, Size: 5
    at java.util.ArrayList.rangeCheck(Unknown Source) ~[?:1.7.0_79]
    at java.util.ArrayList.get(Unknown Source) ~[?:1.7.0_79]
    at xyz.lexium.brocubes.drops.DropDB.getRandomDrop(DropDB.java:17) ~[DropDB.class:?]
    at xyz.lexium.brocubes.blocks.BroBlock.onBlockDestroyedByPlayer(BroBlock.java:33) ~[BroBlock.class:?]
    at net.minecraft.client.multiplayer.PlayerControllerMP.onPlayerDestroyBlock(PlayerControllerMP.java:187) ~[PlayerControllerMP.class:?]
    at net.minecraft.client.multiplayer.PlayerControllerMP.func_178891_a(PlayerControllerMP.java:68) ~[PlayerControllerMP.class:?]
    at net.minecraft.client.multiplayer.PlayerControllerMP.func_180511_b(PlayerControllerMP.java:232) ~[PlayerControllerMP.class:?]
    at net.minecraft.client.Minecraft.clickMouse(Minecraft.java:1519) ~[Minecraft.class:?]
    at net.minecraft.client.Minecraft.runTick(Minecraft.java:2126) ~[Minecraft.class:?]
    at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:1087) ~[Minecraft.class:?]
    at net.minecraft.client.Minecraft.run(Minecraft.java:376) [Minecraft.class:?]
    at net.minecraft.client.main.Main.main(Main.java:117) [Main.class:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_79]
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.7.0_79]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.7.0_79]
    at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.7.0_79]
    at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.12.jar:?]
    at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_79]
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.7.0_79]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.7.0_79]
    at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.7.0_79]
    at net.minecraftforge.gradle.GradleStartCommon.launch(Unknown Source) [start/:?]
    at GradleStart.main(Unknown Source) [start/:?]

The code I use for this is:

DropBase drop = DropDB.getRandomDrop();
for (int i = 1; i < drop.getDrops().size() -1; i++) {
    EntityItem item = new EntityItem(worldIn, pos.getX(), pos.getY() + 1, pos.getZ(), drop.getDrops().get(i));
    System.out.println(i);
    worldIn.spawnEntityInWorld(item);

This code calls DropDB and selects a random drop from a registered list. The list is perfectly fine. Here is the code for getDrop is:

 public static DropBase getRandomDrop() {
     Random rand = new Random();
        int n = rand.nextInt(drops.size()) + 1;
        System.out.println(n);
        System.out.println(drops.size());
        return drops.get(n);
    }

This code causes this error. I have tired to look at the other questions around here. They have not worked.

Answer 1

Indices in Java are 0-based the valid values are 0 to size() - 1 . When you generate a new random number you should not + 1 you want a range of 0 to size() -1 .

Answer 2

I was having similar issues with an array. I believe it has to do with the for loop itself, quite not sure though, feel free to correct. The equivalent of what solved my issue would be this :

Look at this part

for (int i = 1; i < drop.getDrops().size() -1; i++) 

I would do this instead :

Int dropsSize = drop.getDrops().size() - 1;  // just to keep it clean 
                                             // but you don't have to do this.
for (int **i = 0**; i < dropsSize ; i++) {