end island location source code

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 int max = 0;
    private static List<BlockPos> startPortals = new ArrayList<>();

    public static void main(String[] args) {
        final int MIN_RADIUS = 768 - 16;
        final int MAX_RADIUS = 1024 + 16;
        for (int x = -MAX_RADIUS; x <= MAX_RADIUS; x++) {
            System.out.println(x);
            for (int z = -MAX_RADIUS; z <= MAX_RADIUS; z++) {
                if (x * x + z * z <= MAX_RADIUS * MAX_RADIUS && x * x + z * z >= MIN_RADIUS * MIN_RADIUS) {
                    doStuffWithPortal(x, z);
                }
            }
        }

        startPortals.sort(Comparator.<BlockPos>comparingDouble(portal -> {
            double angle = Math.atan2(portal.z, portal.x);
            angle *= 20 / (Math.PI * 2);
            double rounded = Math.round(angle);
            return Math.abs(rounded - angle);
        }));

        System.out.println("Found " + startPortals.size() + " max portals");
        System.out.println("Max size: " + max);
        startPortals.forEach(pos -> System.out.println(pos.x + ", " + pos.z));
    }

    public static void doStuffWithPortal(int portalX, int portalZ) {
        double distance = Math.sqrt(portalX * portalX + portalZ * portalZ);

        double normX = portalX / distance;
        double normZ = portalZ / distance;

        double x = normX * 768;
        double z = normZ * 768;

        doStuffWithExitPortal(portalX, portalZ, (int) Math.round(x), (int) Math.round(z));
    }

    public static void doStuffWithExitPortal(int startX, int startZ, int portalX, int portalZ) {
        //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)portalX & X_MASK) << X_SHIFT | ((long)75 & Y_MASK) << Y_SHIFT | ((long)portalZ & Z_MASK) << 0;
        //System.out.println(seed);
        Set<BlockPos> endStone = new HashSet<>();
        generate(new Random(seed), endStone);
        int count = endStone.size();
        if (count > max) {
            max = count;
            startPortals.clear();
        }
        if (count == max) {
            startPortals.add(new BlockPos(startX, 0, startZ));
        }
    }

    public static boolean generate(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(j, i, k));
                    }
                }
            }

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

        return true;
    }

    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;
        }
    }

}