Scanner sc = new Scanner(System.in);
    boolean loop = false, restart = false;
    String input;
    int base;
    do{
        do{
            System.out.print("Enter base 10 value: ");
            input = sc.next();
            if(Integer.parseInt(input)<0){
                System.out.println("Invalid decimal number: "+input);
                loop = true;
            }else{
                loop=false;
            }
        }while(loop==true);
        do{
            System.out.print("Enter base to convert to: ");
            base = sc.nextInt();
            if(base>36){
                System.out.println("Invalid radix: "+base);
                loop = true;
            }else if(base<2){
                System.out.println("Invalid radix: "+base);
                loop = true;
            }else{
                loop = false;
            }
        }while(loop==true);
        String converted = convertBase(input,base);
        System.out.print(input+" in base "+base+" is "+converted);
        System.out.println();
        System.out.print("New Conversion? (y/n): ");
        if(sc.next().equals("y")){
            restart = true;
        }else{
            restart = false;
        }
    }while(restart == true);

public static String convertBase(String number, int targetBase){
    String converted = "";
    int temp = Integer.parseInt(number);
    int power = largestPower(temp, targetBase);
    int product[] = new int[power+1];
    int remain = temp;
    int j = 0;
    for(int i = power; i>=0;i--){
        product[j] =remain/( (int) Math.pow(targetBase, i));
        if(product[j]!=0){
            remain -= product[j]*Math.pow(targetBase, i);
        }
        j++;
    }
    char ascii;
    if(targetBase>=16){
        for(int k : product) {
            if(k>=10){
                k+=55;
                ascii = (char)k;
                converted+=ascii;
                }else{
                    converted+=k;
                }
            }
    }else{
        for(int i : product) {
                converted+=i;
                }
    }
    return converted;
}

public static int largestPower(int x, int target)
   {
        int power = 1;
        for (int i = target; i< x; i*=target){
            power++;
        }
        if(Math.pow(target, power)>x){
            power--;
        }
        return power;
   }