First Convert the structs to classes with public attributes i.e.

1. public class CityType {
2.   public  int x;
3.   public  int y;
4. }
5. 
   
6. public class AntType {
7.   public int curCity;
8.   public int nextCity;
9.   public short tabu[MAX_CITIES];
10.   public int pathIndex;
11.   public short path[MAX_CITIES];
12.   public double tourLength;
13. }

Note: I have capatalised the class names because that is a convention in Java also that I have changed the unsigned char data types to short since Java does not have unsigned data types.

This line will create an array of 1000 CityType objects.

CityType[] cities = new CityType[1000];

The following lines will work although you would have to ensure that

1. cities[from].x = getRand( MAX_DISTANCE );
2. cities[from].y = getRand( MAX_DISTANCE );

If the getRand function returns a floating point number then you will have to cast the result to an int i.e.

1. cities[from].x = (int) getRand( MAX_DISTANCE );
2. cities[from].y = (int) getRand( MAX_DISTANCE );

just a question by the way.

When I use the class

Do I have to write

1. cities[from].x
2. cities[from].y
3. cities[from].name

etc.
or is there a with.structure in processing allowing

1. with cities[from]
2.    .x
3.    .y
4.    .name

?

Thank you!

Thank you!

Hi

 

Thanks to every one for your answers and I want to apologize for no thank you before. The true is I’m a beginner in programming processing with C++ and I want to do an application using this.

 

Well, I´ve wrote my code as quarks said it but something goes wrong :

NullPointerException, in this line cities [from].x = (int)(getRand(MAX_DISTANCE));, I assume that is related with the x pointer.

 

This is a piece of the code:

 

int MAX_CITIES = 15;

float MAX_DISTANCE = 100.0;

float MAX_TOUR = (MAX_CITIES * MAX_DISTANCE);

int MAX_ANTS = 2*MAX_CITIES;

 

float ALPHAA = 0.5;

float BETA = 0.6;

float RHO = 0.9;              /* Intensity / Evaporation */

 

int QVAL = 100;

int MAX_TOURS = 500;

int MAX_TIME = (MAX_TOURS * MAX_CITIES);

float INIT_PHEROMONE = (1.0 / MAX_CITIES);

float RAND_MAX = 100.0;

 

// Clases

 

CityType[] cities = new CityType[MAX_CITIES];

//AntType[] ants = new AntType[MAX_ANTS];

 

public class CityType{

  public int x;

  public int y;

}

/*public class AntType{

  public int curCity;

  public int nextCity;

  public short[] tabu = new short[MAX_CITIES];

  public int pathIndex;

  public short[] path = new short[MAX_CITIES];

  public double tourLength;

}*/

 

// End, Class

                                /*   From          To     */

float[][] distance = new float[MAX_CITIES][MAX_CITIES];

                              /*    From         To      */

float[][] pheromone = new float[MAX_CITIES][MAX_CITIES];

double  best=(double)MAX_TOUR;

int bestIndex;

 

void Init(){

  int from= 0;

  int to = 0;

  int ant = 0;

  int xd = 0;

  int yd = 0;

 

 

  //Create the cities and their locations

  for (from = 0; from<MAX_CITIES; from++){

    //Randomly place cities around the grid

    cities[from].x = (int)(getRand(MAX_DISTANCE));   //  in this line I have the error

    cities[from].y = (int)(getRand(MAX_DISTANCE));

    for (to = 0; to<MAX_CITIES; to++){

      distance[from][to] = 0.0;

      pheromone[from][to] = INIT_PHEROMONE;

    }

  }

 

  // Compute the distances for each of the cities on the map

  for ( from = 0 ; from < MAX_CITIES ; from++) {

    for ( to = 0 ; to < MAX_CITIES ; to++) {

      if ((to != from) && (distance[from][to] == 0.0)) {

        xd = abs(cities[from].x - cities[to].x);

        yd = abs(cities[from].y - cities[to].y);

        distance[from][to] = sqrt( (xd * xd) + (yd * yd) );

        distance[to][from] = distance[from][to];

      }

    }

  }

  // Initialize the ants

  to = 0;

  for ( ant = 0 ; ant < MAX_ANTS ; ant++ ){

    // Distribute the ants to each of the cities uniformly

    if (to == MAX_CITIES) to = 0;

    ants[ant].curCity = to++;

    for ( from = 0 ; from < MAX_CITIES ; from++ ) {

      ants[ant].tabu[from] = 0;

      ants[ant].path[from] = -1;

    }

    ants[ant].pathIndex = 1;

    ants[ant].path[0] = (short)(ants[ant].curCity);

    ants[ant].nextCity = -1;

    ants[ant].tourLength = 0.0;

    // Load the ant's current city into taboo

    ants[ant].tabu[ants[ant].curCity] = 1;

 

  } 

}

 

float getSRand(){

  return (random(RAND_MAX) / RAND_MAX);

}

float getRand(float x){

  float Ran = x*random(RAND_MAX)/(RAND_MAX+1.0);

  return Ran; //(int)(x*random(RAND_MAX)/(RAND_MAX+1.0));

}

 

Unlike C++, Java fills the arrays with null, ie. with nothing. The arrays doesn't allocate the space for the structures, but only for references to objects to be creates (roughly equivalent to pointers).
So you have to create one object for each slot of the array: cities[from] = new CityType(); before using x or y.