river modified, Java

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//'main' method must be in a class 'Rextester'.
//Compiler version 1.8.0_72

import java.util.*;
class Rextester{
  static String c(int i){
    if(i <= 0){
      return "";
    }
    ArrayList<Long> r = f(1),
                    s = f(3),
                    t = f(9),
                    x = f(i);
    String z = "first meets river ",
           y = " at ";
    for(int j = 0; j < r.size(); j++){
      long u = r.get(j),
           v = s.get(j),
           w = t.get(j);
      if(x.contains(u)){
        return z+1+y+u;
      }
      if(x.contains(v)){
        return z+3+y+v;
      }
      if(x.contains(w)){
        return z+9+y+w;
      }
    }
    return "";
  }

static ArrayList<Long> f(long i){
    ArrayList<Long> l = new ArrayList<Long>();
    l.add(i);
    for(long j = 0, x; j < 9e4; j++){
      x = l.get(l.size() - 1);
      for(char c : (x + "").toCharArray()){
        x += Character.getNumericValue(c);
      }
      l.add(x);
      if(x > 16383){
        return l;
      }
    }
    return l;
  }

public static void main(String[] a){
    System.out.println(c(86));
    System.out.println(c(12345));
    System.out.println(c(0));
  }
}

[ + ] Show input
Compilation time: 0.62 sec, absolute running time: 0.14 sec, cpu time: 0.11 sec, memory peak: 22 Mb, absolute service time: 0,77 sec