Thread: Help with methods and constructors please!

Main class

 /**
 * The class TrainClient tests Train class. A number of orders is made and then carriage map is printed.
 **/
public class TrainClient {
 
  /**  Number of rows in a carriage **/
  public static final int NUMBER_OF_ROWS = 3;
 
  /**  Number of columns in a carriage **/
  public static final int NUMBER_OF_COLUMNS = 4;
 
  public static void main(String[] args) {
 
    // On this train the ordering of seats is made
    Train train = new Train();
 
    // Set carriages
    for(int i = 0; i < Train.MAX_NUMBER_OF_CARRIAGES;i++){
      train.setInCarriage(new Carriage(NUMBER_OF_ROWS,NUMBER_OF_COLUMNS));
    }
 
    // orderMap shows what orders have to be made in the train. 
    //In each row, the first value is the number of the carriag and the secind value is the column number.
    int[][] orderMap =
      {{0,0},
       {1,1},
       {1,1},
       {0,2},
       {2,3},
       {2,0},
       {3,4},
       {-1,-1},
       {0,0},
       {0,0},
       {0,0},
       {0,-1},
       {0,5},
       {2,1}
       };
 
    // Does the orders in orderMap
    for(int i = 0; i < orderMap.length;i++){
      int carriageNr = orderMap[i][0];
      int column = orderMap[i][1];
 
      train.orderSeat(carriageNr,column);
    }
 
    System.out.println();
    System.out.println("Seatmap for the train after reservation");
 
    // Prints out carriagemap for all carriages.
    for(int i = 0; i < Train.MAX_NUMBER_OF_CARRIAGES;i++){
      System.out.printf("%nCarriage %d:%n",i);
      train.printOutMap(i); 
    }
  }
}

Help classes

Train

/**
 *  The class train is administering the ordering of seats.
 *  - A train is implemented as an array of carriages.
 *  - The number of carriages is relative to how many carriages are set.
 **/
public class Train {
 
  /** Max number of carriages */
  public final static int MAX_NUMBER_OF_CARRIAGES = 3;
 
 
  private Carriage[] carriages;    // Array of carriages
  private int numberOfCarriages; // Number of carriages
 
  /**
   * Konstruktøren oppretter en tabell for vogner.
   **/
  public Train() {
    numberOfCarriages = 0;
    carriages = new Carriage[MAX_NUMBER_OF_CARRIAGES];
  }
 
  public int getTheNumberOfCarriages() {
    return numberOfCarriages;
  }
 
  /**
   * @param carriage Carriage to set into the array of carriages.
   * @return true if the given carriage was sat in, otherwise false.
   **/
  public boolean setInCarriage(Carriage carriage) {
    // WHAT IS THE CODE FOR THIS METHOD?
 
  }
 
 
  /**
   * Method does the following
   *  - If CarriageNr is not valid, the program gives an error message.
   *  - Reserves the first empty seat in the given column.
   *  - Prints out the row, column and the carriageNr of the reserved seat.
   * For example:
   * Carriage Nr. 2, Seat[1, 3].
   * @param CarriageNr Number of the carriage where the seat is ordered.
   * @param column preferred column.
   * @return true if the seat has been ordered.
   **/
  public boolean orderSeat(int carriageNr, int column) {
    // WHAT IS THE CODE FOR THIS METHOD?
 
  }
 
  /**
   * Prints out the seatmap of the carriage with the given carriage Nr.
   * @param carriageNr The number of the carriage to print out the seatmap for.
   * @return true if the seatmap has been printed, false if there is no carriage with the given Nr.
   **/
  public boolean printOutMap(int carriageNr){
    if(carriageNr >= numberOfCarriages || carriageNr < 0){
      return false;
    }
 
    carriages[carriageNr].drawSeatMap();
    return true;
 
  }
}

Carriage

/**
 * The Class Carriage represents a carriage in a train.
 * - A carriage has a plan (given with a number of rows and a number of columns).
 * - A 2D array holds the order of how many empty seats in every column.
 */
public class Carriage {
 
  private int         numberOfRows;          // Number of rows in a carriage
  private int         numberOfColumns;       // Number of columns in the carriage
  private boolean[][] carriagePlan;          // Defines what seats are taken
  private int[]       numberOfEmptySeats;    // Number of empty seats for every column.
 
  /**
   * The constructor does the following:
   * - makes the plan (where no seats are reserved).
   * - initialises the array of the number of empty seats in every column.
   * - initialising of the field variables
   * @param rows        gives the number of rows in the carriage.
   * @param columns     gives the number of columns in the carriage.
   */ 
  public Carriage(int rows, int columns) {
    // WHAT IS THE CODE FOR THIS CONSTRUCTOR?
 
 
  }
 
  /**
   * Sets the place given by (i,j)-pair i the plan to "taken".
   * Creates the number of available seats of the column given by a column nr.
   * @param i shows the row nr of this seat.
   * @param j shows the column nr for this seat. 
   **/
  private void setTaken(int i, int j) {
    // WHAT IS THE CODE FOR THIS METHOD?
  }
 
  /**
   * Deloppgave 2c
   * @return nr of the first empty seat available.
   *         if there are no empty seats in the column return -1.
   **/
  private int findRowNrOfTheFirstEmptySeat(int column) {
    // WHAT IS THE CODE FOR THIS METHOD?
  }
 
  /**
   * Metoden reserverer den første ledige plassen av den angitte kolonnen.
   * This method reserves the first empty seat of the given column.
   * If the given column is not valid or if there are no empty seats, an error message is given.
   * and -1 is returned.
   * @return Row nr of the first empty seat of the given column that was reserved, otherwise -1.
   **/
  public int reserveTheFirstEmptySeat(int column) {
    // WHAT IS THE CODE FOR THIS METHOD?
  }
 
  /**
   * Draws the plan for the carriage.
   * A taken seat is given by "+", an empty seat is given by "-".
   * For example:
   *   012
   * 0 -++
   * 1 -+-
   **/
  public void drawSeatMap() {
    // WHAT IS THE CODE FOR THIS METHOD?
  }
}

How do I code the missing methods and the constructor? What the methods and the constructor needs to do, is written as comments in the classes. I really apreaciate your help!