Possibly fixed crashes caused by tile entities under certain circumstances again.

src/main/java/net/minecraft/server/TileEntityPiston.java

@@ -0,0 +1,130 @@
+package net.minecraft.server;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+public class TileEntityPiston extends TileEntity {
+
+    private int a;
+    private int b;
+    private int c;
+    private boolean i;
+    private boolean j;
+    private float k;
+    private float l;
+    private static List m = new ArrayList();
+
+    public TileEntityPiston() {}
+
+    public TileEntityPiston(int i, int j, int k, boolean flag, boolean flag1) {
+        this.a = i;
+        this.b = j;
+        this.c = k;
+        this.i = flag;
+        this.j = flag1;
+    }
+
+    public int a() {
+        return this.a;
+    }
+
+    public int e() {
+        return this.b;
+    }
+
+    public boolean c() {
+        return this.i;
+    }
+
+    public int d() {
+        return this.c;
+    }
+
+    public float a(float f) {
+        if (f > 1.0F) {
+            f = 1.0F;
+        }
+
+        return this.l + (this.k - this.l) * f;
+    }
+
+    private void a(float f, float f1) {
+        if (!this.i) {
+            --f;
+        } else {
+            f = 1.0F - f;
+        }
+
+        AxisAlignedBB axisalignedbb = Block.PISTON_MOVING.a(this.world, this.x, this.y, this.z, this.a, f, this.c);
+
+        if (axisalignedbb != null) {
+            List list = this.world.b((Entity) null, axisalignedbb);
+
+            if (!list.isEmpty()) {
+                m.addAll(list);
+                Iterator iterator = m.iterator();
+
+                while (iterator.hasNext()) {
+                    Entity entity = (Entity) iterator.next();
+
+                    entity.move((double) (f1 * (float) PistonBlockTextures.b[this.c]), (double) (f1 * (float) PistonBlockTextures.c[this.c]), (double) (f1 * (float) PistonBlockTextures.d[this.c]));
+                }
+
+                m.clear();
+            }
+        }
+    }
+
+    public void k() {
+        if (this.l < 1.0F) {
+            this.l = this.k = 1.0F;
+            this.world.o(this.x, this.y, this.z);
+            this.h();
+            if (this.world.getTypeId(this.x, this.y, this.z) == Block.PISTON_MOVING.id) {
+                this.world.setTypeIdAndData(this.x, this.y, this.z, this.a, this.b);
+            }
+        }
+    }
+
+    public void g_() {
+        // CraftBukkit
+        if (this.world == null) return;
+        this.l = this.k;
+        if (this.l >= 1.0F) {
+            this.a(1.0F, 0.25F);
+            this.world.o(this.x, this.y, this.z);
+            this.h();
+            if (this.world.getTypeId(this.x, this.y, this.z) == Block.PISTON_MOVING.id) {
+                this.world.setTypeIdAndData(this.x, this.y, this.z, this.a, this.b);
+            }
+        } else {
+            this.k += 0.5F;
+            if (this.k >= 1.0F) {
+                this.k = 1.0F;
+            }
+
+            if (this.i) {
+                this.a(this.k, this.k - this.l + 0.0625F);
+            }
+        }
+    }
+
+    public void a(NBTTagCompound nbttagcompound) {
+        super.a(nbttagcompound);
+        this.a = nbttagcompound.e("blockId");
+        this.b = nbttagcompound.e("blockData");
+        this.c = nbttagcompound.e("facing");
+        this.l = this.k = nbttagcompound.g("progress");
+        this.i = nbttagcompound.m("extending");
+    }
+
+    public void b(NBTTagCompound nbttagcompound) {
+        super.b(nbttagcompound);
+        nbttagcompound.a("blockId", this.a);
+        nbttagcompound.a("blockData", this.b);
+        nbttagcompound.a("facing", this.c);
+        nbttagcompound.a("progress", this.l);
+        nbttagcompound.a("extending", this.i);
+    }
+}

src/main/java/net/minecraft/server/World.java

@@ -1144,14 +1144,20 @@ public class World implements IBlockAccess {
                 TileEntity tileentity1 = (TileEntity) iterator1.next();
 
                 if (!tileentity1.g()) {
-                    if (!this.c.contains(tileentity1)) {
+                    // CraftBukkit - order matters, moved down
+                    /* if (!this.c.contains(tileentity1)) {
                         this.c.add(tileentity1);
-                    }
+                    } */
 
                     Chunk chunk1 = this.getChunkAt(tileentity1.x >> 4, tileentity1.z >> 4);
 
                     if (chunk1 != null) {
                         chunk1.a(tileentity1.x & 15, tileentity1.y, tileentity1.z & 15, tileentity1);
+                        // CraftBukkit start - moved in from above
+                        if (!this.c.contains(tileentity1)) {
+                            this.c.add(tileentity1);
+                        }
+                        // CraftBukkit end
                     }
 
                     this.notify(tileentity1.x, tileentity1.y, tileentity1.z);
@@ -1539,8 +1545,8 @@ public class World implements IBlockAccess {
 
                 if (chunk != null) {
                     chunk.a(i & 15, j, k & 15, tileentity);
+                    this.c.add(tileentity); // CraftBukkit - moved in from above
                 }
-                this.c.add(tileentity);
             }
         }
     }