why cant my statement parse string to integer?

Question

I am trying to parse a string to integer but I get incompatible types. My counter is for the amount of records that are in the file, the program can append to the file and read from it. now I want to sort it and write it back to file. How can I perform this task? variables that are not declared here are dclared globally.

public static void sort_addresses() throws IOException
{
 String tnumber;
 String tname;
 String tnrooms;
 int[] tmprooms;
 int[] tmprooms1;
 int j;
 for (int i = 0; i < counter; i++)
 {
    for(j = 1; j < (counter-1); j++)
    //while (street_name[counter] != null)
    {
        tmprooms = Integer.parseInt (number_rooms[counter]); 
        tmprooms1 = Integer.parseInt (number_rooms[counter+1]); 
        if (tmprooms[i] > tmprooms1[i+1])
        {
            tnumber = street_number[counter];
            tname =  street_name[counter];
            tnrooms = number_rooms[counter];
            street_number[counter] = street_number[counter +1];
            street_name[counter] = street_name[counter+1];
            number_rooms[counter] = number_rooms[counter+1];
            number_rooms[counter+1] = tnumber ;
            street_name[counter+1] = tname;
            number_rooms[counter+1] = tnrooms;
            System.out.println(street_number[i]+"\t"+street_name[i]
                +"\t"+number_rooms[i]);
        }
    }

Answer 1

Declare:

  int[] tmprooms;
  int[] tmprooms1;

as

  int tmprooms;
  int tmprooms1;

Integer#parseInt() returns an int , not an int[] .

Answer 2

try this

public static void sort_addresses() throws IOException
    {
     String tnumber;
     String tname;
     String tnrooms;
     int tmprooms;
     int tmprooms1;
     int j;
     for (int i = 0; i < counter; i++)
     {
        for(j = 1; j < (counter-1); j++)
        //while (street_name[counter] != null)
        {
            tmprooms = (Integer)number_rooms[counter]; 
            tmprooms1 = (Integer)number_rooms[counter+1]; 
            if (tmprooms[i] > tmprooms1[i+1])
            {
                tnumber = street_number[counter];
                tname =  street_name[counter];
                tnrooms = number_rooms[counter];
                street_number[counter] = street_number[counter +1];
                street_name[counter] = street_name[counter+1];
                number_rooms[counter] = number_rooms[counter+1];
                number_rooms[counter+1] = tnumber ;
                street_name[counter+1] = tname;
                number_rooms[counter+1] = tnrooms;
                System.out.println(street_number[i]+"\t"+street_name[i]
                    +"\t"+number_rooms[i]);
            }
        }

Answer 3

Integer.parseInt() returns an int (which can be auto-boxed to an Integer), not an int[] array.

The variable tmprooms is of the type int[], but Integer.parseInt() does not return an int[] array.

The following can be used to sort an int[] array:

Arrays.sort(int [])

Please see the following: Arrays#sort(int[])

Answer 4

A few things:

• tmprooms and tmprooms1 need to be int's, not int[]'s.
• j needs to start from 0.
• You need to use j, not counter for array accesses.
• The System.out.println where it is doesn't really print anything meaningful.
• number_rooms[counter+1] = tnumber; should be street_number[counter+1] = tnumber;
• This appears to be Bubble sort, just without stopping early (thus even less efficient than the already inefficient algorithm). There are far better algorithms out there, like the one used by Arrays.sort (see below).

Final code:

public static void sort_addresses()
{
  String snumber, sname, tnrooms;
  int tmprooms, tmprooms1;
  for (int i = 0; i < counter; i++)
  {
     for (int j = 0; j < counter - 1; j++)
     {
        tmprooms = Integer.parseInt(number_rooms[j]);
        tmprooms1 = Integer.parseInt(number_rooms[j + 1]);
        if (tmprooms > tmprooms1)
        {
           snumber = street_number[j];
           sname = street_name[j];
           tnrooms = number_rooms[j];
           street_number[j] = street_number[j + 1];
           street_name[j] = street_name[j + 1];
           number_rooms[j] = number_rooms[j + 1];
           street_number[j + 1] = snumber;
           street_name[j + 1] = sname;
           number_rooms[j + 1] = tnrooms;
        }
     }
  }
}

Test.

A better way using objects: (allowing you to use Arrays.sort)

static class Address
{
  int numberOfRooms;
  String streetNumber;
  String streetName;

  Address(String streetName, String streetNumber, int numberOfRooms)
  {
     this.numberOfRooms = numberOfRooms;
     this.streetName = streetName;
     this.streetNumber = streetNumber;
  }

  @Override
  public String toString()
  {
     return numberOfRooms + ":" + streetName + ":" + streetNumber;
  }

  // an alternative is to have the class "implements Comparable<Address>"
  //   and have a "public int compareTo(Address o)" function
  //   then you can just say "Arrays.sort(addresses)"
  public static Comparator<Address> numberOfRoomsComparator
     = new Comparator<Address>() {
        @Override
        public int compare(Address o1, Address o2)
        {
          return Integer.valueOf(o1.numberOfRooms).compareTo(o2.numberOfRooms);
        }
     };
}

static Address[] addresses = {new Address("u1", "a1", 3),
                              new Address("u2", "a2", 1),
                              new Address("u3", "a3", 5),
                              new Address("u4", "a4", 4),
                              new Address("u5", "a5", 2)};

public static void main(String[] args)
{
  Arrays.sort(addresses, Address.numberOfRoomsComparator);
  System.out.println(Arrays.toString(addresses));
}