Consistent hash by using Google Guava

HashingTest.java

import com.google.common.hash.Hashing;
import org.junit.Test;

import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;

public class HashingTest {
    @Test
    public void consistentHashing() {
        int buckets = 3;
        int tenants = 10;

        Map<Integer, Set<Long>> output1 = new HashMap<>();

        for (int i=0; i<tenants; i++) {
            int output = Hashing.consistentHash(i, buckets);
            output1.putIfAbsent(output, new LinkedHashSet<>());
            output1.get(output).add(Long.valueOf(i));
        }

        System.out.println(output1);


        // add a new bucket.
        buckets = 4;
        Map<Integer, Set<Long>> output2 = new HashMap<>();

        for (int i=0; i<tenants; i++) {
            int output = Hashing.consistentHash(i, buckets);
            output2.putIfAbsent(output, new LinkedHashSet<>());
            output2.get(output).add(Long.valueOf(i));
        }

        System.out.println(output2);

        //{0=[0, 1, 2, 7, 8], 1=[4, 5], 2=[3, 6, 9]}
        //{0=[0, 1, 7, 8], 1=[4, 5], 2=[6, 9], 3=[2, 3]}
    }
}