FibonacciController.java

package com.example;
 
import io.micronaut.http.MediaType;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;
import java.util.HashMap;
import java.util.Map;
 
@Controller("/")
public class FibonacciController {
 
    private static final StringBuilder LOG = new StringBuilder();
    private static final Map<Integer, Long> CACHE = new HashMap();
     
    @Get(uri = "/nthFibonacci/{nth}", produces = MediaType.TEXT_PLAIN)
    public String nthFibonacci(Integer nth) {
        long[] counter = new long[] {0};
        long start = System.currentTimeMillis();
 
        LOG.append("Fibonacci number #").append(nth).append(" is ");
        LOG.append(computeNthFibonacci(nth, counter));
        LOG.append(" (computed in ").append(System.currentTimeMillis() - start).append(" ms, ").append(counter[0]).append(" steps)\n");
 
        return LOG.toString();
    }
 
    private static long computeNthFibonacci(int nth, long[] counter) {
        counter[0]++;
         
        if (nth == 0 || nth == 1) return nth;
         
        Long result = CACHE.get(nth);
        if (result == null) {
            result = computeNthFibonacci(nth - 1, counter) + computeNthFibonacci(nth - 2, counter);
            CACHE.put(nth, result);
        }
        return result;
    }
 
}