Fix double overflow/underflow calculations with explosions. Fixes BUKKIT-1865

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

@@ -108,17 +108,26 @@ public class Explosion {
 
         for (int k2 = 0; k2 < list.size(); ++k2) {
             Entity entity = (Entity) list.get(k2);
-            double d7 = entity.f(this.posX, this.posY, this.posZ) / (double) this.size;
-
-            if (d7 <= 1.0D) {
+            // CraftBukkit - start
             d0 = entity.locX - this.posX;
             d1 = entity.locY - this.posY;
             d2 = entity.locZ - this.posZ;
-                double d8 = Math.sqrt(d0 * d0 + d1 * d1 + d2 * d2); // CraftBukkit
+            double d8 = Math.sqrt(d0 * d0 + d1 * d1 + d2 * d2);
 
+            double d7 = d8 / this.size; // Don't call sub-method and sqrt again
+
+            if (d7 <= 1.0D) {
+                // Moved calculations up
+                if (d8 != 0) {
                     d0 /= d8;
                     d1 /= d8;
                     d2 /= d8;
+                } else { // Compensate for underflow
+                    d0 = 0d;
+                    d1 = 0d;
+                    d2 = 0d;
+                }
+                // CraftBukkit - end
                 double d9 = (double) this.world.a(vec3d, entity.boundingBox);
                 double d10 = (1.0D - d7) * d9;