end island code

package test;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashSet;
import java.util.List;
import java.util.Random;
import java.util.Set;

public class Main {

    private static List<EndIsland> endIslands = new ArrayList<>();

    public static void main(String[] args) {
        List<BlockPos> positions = new ArrayList<>();
        for (int x = -768; x <= 768; x++) {
            for (int z = -768; z <= 768; z++) {
                if (Math.round(Math.sqrt(x * x + z * z)) == 768) {
                    positions.add(new BlockPos(x, 0, z));
                }
            }
        }

        System.out.println("Positions on the perimeter: " + positions.size());
        for (BlockPos pos : positions)
            doStuffWithExitPortal(pos.x, pos.z);

        endIslands.sort(Comparator.comparing(island -> -island.usableEndStone));

        int i = 0;
        for (EndIsland island : endIslands) {
            System.out.println("(" + island.x + ", " + island.z + ") " + island.usableEndStone + " usable out of " + island.totalEndStone + " total");
            i++;
            if (i > 200)
                break;
        }
    }

    public static void doStuffWithExitPortal(int islandX, int islandZ) {
        //System.out.println(portalX + ", " + portalZ);

        final int NUM_X_BITS = 26;
        final int NUM_Z_BITS = NUM_X_BITS;
        final int NUM_Y_BITS = 64 - NUM_X_BITS - NUM_Z_BITS;
        final int Y_SHIFT = 0 + NUM_Z_BITS;
        final int X_SHIFT = Y_SHIFT + NUM_Y_BITS;
        final long X_MASK = (1L << NUM_X_BITS) - 1L;
        final long Y_MASK = (1L << NUM_Y_BITS) - 1L;
        final long Z_MASK = (1L << NUM_Z_BITS) - 1L;
        long seed = ((long)islandX & X_MASK) << X_SHIFT | ((long)75 & Y_MASK) << Y_SHIFT | ((long)islandZ & Z_MASK) << 0;
        //System.out.println(seed);
        Set<BlockPos> endStone = new HashSet<>();
        generate(islandX, islandZ, new Random(seed), endStone);

        int totalCount = endStone.size();
        int chunkX = islandX >> 4, chunkZ = islandZ >> 4;
        int usableCount = 0;
        for (BlockPos pos : endStone) {
            if (pos.x >> 4 != chunkX || pos.z >> 4 != chunkZ) {
                if (pos.x != islandX && pos.z != islandZ) {
                    usableCount++;
                }
            }
        }

        endIslands.add(new EndIsland(islandX, islandZ, totalCount, usableCount));
    }

    public static boolean generate(int x, int z, Random rand, Set<BlockPos> endStone) {
        float f = (float) (rand.nextInt(3) + 4);

        for (int i = 0; f > 0.5F; --i) {
            for (int j = (int) Math.floor(-f); j <= Math.ceil(f); ++j) {
                for (int k = (int) Math.floor(-f); k <= Math.ceil(f); ++k) {
                    if ((float) (j * j + k * k) <= (f + 1.0F) * (f + 1.0F)) {
                        endStone.add(new BlockPos(x + j, i, z + k));
                    }
                }
            }

            f = (float) ((double) f - ((double) rand.nextInt(2) + 0.5D));
        }

        return true;
    }

    public static class EndIsland {
        private int x;
        private int z;
        private int totalEndStone;
        private int usableEndStone;

        public EndIsland(int x, int z, int totalEndStone, int usableEndStone) {
            this.x = x;
            this.z = z;
            this.totalEndStone = totalEndStone;
            this.usableEndStone = usableEndStone;
        }
    }

    public static class BlockPos {
        private int x, y, z;

        public BlockPos(int x, int y, int z) {
            this.x = x;
            this.y = y;
            this.z = z;
        }

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result + x;
            result = prime * result + y;
            result = prime * result + z;
            return result;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj)
                return true;
            if (obj == null)
                return false;
            if (getClass() != obj.getClass())
                return false;
            BlockPos other = (BlockPos) obj;
            if (x != other.x)
                return false;
            if (y != other.y)
                return false;
            if (z != other.z)
                return false;
            return true;
        }
    }

}