Array overflow

I have this overflow problem in an array that I have within several objects.

  

java.lang.ArrayIndexOutOfBoundsException: 7       at Exercise.Visiting.run (Visitor.java:73)

The code

public class Visitor extends Thread {

private String salaReg[];
private String salaRegAnt[];
private Semaphore sem;
private String id;
private Room sala[];

public Visitante(String id, Room sala[], Semaphore sem) {
    this.id = id;
    this.sala = sala;
    this.sem = sem;
}

@Override
public void run() {
    boolean listo = true;
    boolean existe = true;
    int j = 0;
    int k = 0;
    int numRan;

    try {

        sem.acquire();
        System.out.println("/////////////////HILO " + id);
        System.out.println("Estoy en sala " + sala[0].getId());
        salaReg = sala[0].getReg();
        System.out.println("Actual");
        for (int m = 0; m < salaReg.length; m++) {
            System.out.printf(salaReg[m] + " | ");
        }

        while (listo) {
            if (salaReg[j].equals(" ")) {
                salaReg[j] = id;
                sala[0].setReg(salaReg);
                listo = false;
            } else {
                j++;
            }
        }
        j = 0;
        listo = true;
        numRan = (int) (Math.random() * 2000 + 400);
        Thread.sleep(numRan);

        System.out.println("Museo con " + sala.length + " salas");
        for (int i = 1; i < sala.length; i++) {
            salaReg = null;
            System.out.println("Soy " + id + "  y estoy en sala " + sala[i].getId());

            salaReg = sala[i].getReg();//Array que se supone que debería estar vacio
            //ya que a cada sala del array de salas
            //se le ha "seteado" un array de tipo String
            //con tamaño 7
            //e inicializada a " "

            salaRegAnt = sala[i - 1].getReg();//este array del anterior objeto(por eso i-1)
            //debería tener 1 sólo dato

            System.out.println("Actual");
            for (int m = 0; m < salaReg.length; m++) {
                System.out.printf(salaReg[m] + " | ");
            }
            System.out.println();

            while (listo) {
                if (salaReg[j].equals(" ")) {
                    salaReg[j] = id;
                    sala[i].setReg(salaReg);
                    System.out.println("Antes");
                    for (int m = 0; m < salaRegAnt.length; m++) {
                        System.out.printf(salaRegAnt[m] + " | ");
                    }
                    System.out.println();

                    while (existe) {
                        if (salaRegAnt[k].equals(id)) {
                            salaRegAnt[k] = " ";
                            sala[i - 1].setReg(salaRegAnt);
                            System.out.println("Despues");
                            for (int m = 0; m < salaRegAnt.length; m++) {
                                System.out.printf(salaRegAnt[m] + " | ");
                            }
                            System.out.println();
                            existe = false;
                        } else {
                            k++;
                        }
                    }

                    listo = false;

                } else {
                    j++;
                }
            }
            j = 0;
            k = 0;
            listo = true;
            numRan = (int) (Math.random() * 2000 + 800);
            Thread.sleep(numRan);
        }
        sem.release();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

}

I clarify that in a main class I created an array of String, and that array of String was assigned to an array of objects.

I hope to receive some clarification, since I can not find the fault.