java.lang.NullPointerException

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  • Minecraft crashes when populating a chunk which has empty columns ("void columns"), i.e. colums with just air blocks, no bedrock, such as can for instance be generated by creating a Superflat world with preset {noformat}2;0;1;decoration{noformat} I have attached the crash report. I don't have access to the Minecraft source code, but using the Minecraft Coder Pack for Minecraft 1.7.2 I've traced it to the following code in BiomeDecorator.java (method func_150513_a(BiomeGenBase), lines 160-166): {code} for(var3 = 0; var3 < this.grassPerChunk; ++var3) { var4 = this.chunk_X + this.randomGenerator.nextInt(16) + 8; var5 = this.chunk_Z + this.randomGenerator.nextInt(16) + 8; var6 = this.randomGenerator.nextInt(this.currentWorld.getHeightValue(var4, var5) * 2); WorldGenerator var10 = p_150513_1_.getRandomWorldGenForGrass(this.randomGenerator); var10.generate(this.currentWorld, this.randomGenerator, var4, var6, var5); } {code} It takes the height at a particular x,z coordinate and feeds the result (times two) to Random.nextInt(int). Unfortunately that method throws an exception when passed a value of zero. One way to fix this would be to change those lines to something like: {code} for(var3 = 0; var3 < this.grassPerChunk; ++var3) { var4 = this.chunk_X + this.randomGenerator.nextInt(16) + 8; var5 = this.chunk_Z + this.randomGenerator.nextInt(16) + 8; int height = this.currentWorld.getHeightValue(var4, var5); if (height > 0) { var6 = this.randomGenerator.nextInt(height * 2); WorldGenerator var10 = p_150513_1_.getRandomWorldGenForGrass(this.randomGenerator); var10.generate(this.currentWorld, this.randomGenerator, var4, var6, var5); } } {code} The same would have to be done for the other loops in that method.
    via by Pepijn Schmitz,
    • java.lang.NullPointerException at net.minecraft.server.MinecraftServer.n(SourceFile:299)[1.7.4.jar:?] at btk.n(SourceFile:230)[1.7.4.jar:?] at net.minecraft.server.MinecraftServer.run(SourceFile:389)[1.7.4.jar:?] at lb.run(SourceFile:616)[1.7.4.jar:?]
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