Program in which never leaves the main (infinite loop (?)) [duplicated]

Good, I created a main for a program and the thing is that before adding a bit of code I was doing everything right, when I reached the end of the program I finished the program and everything OK. However, now when the program ends, it does not end, it remains as in an infinite loop from which it does not exit. I leave the main in question:

    public static void main( String [] arg)
{
    int empezar = (int) (Math.random() * 2);
    boolean solucion = false;
    boolean estado;// para saber a quien le toca jugar
    Tablero tablero = new Tablero();
    boolean continuar = true;
    Scanner sca=new Scanner(System.in);
    while (continuar==true)
    {
        if(empezar%2==0)
        {
            estado=false;
        }
        else
        {
            estado=true;
        }
        while(!solucion)
        {
            if(!estado)
            {
                jugador(tablero);
                tablero.ver();
                estado = true;
            }
            else
            {
                maquina(tablero);
                tablero.ver();
                estado = false;
            }
            if(tablero.esSolucion()=='X')
            {
                System.out.println("FELICIDADES JUGADOR 'X'. HAS GANADO A UN SISTEMA DE INTELIGENCIA ARTIFICIAL");
                solucion=true;
            }
            else if(tablero.esSolucion()=='O')
            {
                System.out.println("HAS PERDIDO. LA MAQUINA 'O' TE HA GANADO. TAL VEZ NO SEAS TAN BUENO COMO UN SISTEMA DE INTELIGENCIA ARTIFICIAL");
                solucion=true;
            }
            else if(tablero.esSolucion()==' ')
            {
                System.out.println("HAS EMPATADO CON UN SISTEMA DE INTELIGENCIA ARTIFICIAL. VAS POR EL BUEN CAMINO JOVEN PADAWAN");
                solucion=true;
            }
        }
        System.out.println("Desea jugar otra vez? (1=SI//0=NO)");
        if(sca.nextInt()%2==0)
        {
            System.out.println("NOS VEMOS EN OTRA OCASION. HASTA LUEGO");
            continuar=false;
        }
        else
        {
            System.out.println("Perfecto, empecemos de nuevo.");
            tablero = new Tablero();
            solucion = false;
        }
    }
}

Thanks in advance.

EDIT: I attached the operation of the function 'esSolution ()' since several have told me that it is possible that the error is there.

    public char esSolucion()
{
    char solucion = ' ';

    for(int i = 0; i < 3; i++)
    {
        if(tablero[i][0]=='X'&&tablero[i][1]=='X'&&tablero[i][2]=='X'||tablero[0][i]=='X'&&tablero[1][i]=='X'&&tablero[2][i]=='X')
        {
            solucion='X';
        }
        else if(tablero[i][0]=='O'&&tablero[i][1]=='O'&&tablero[i][2]=='O'||tablero[0][i]=='O'&&tablero[1][i]=='O'&&tablero[2][i]=='O')
        {
            solucion='O';
        }
    }
    if(solucion!='X'&&solucion!='O')
    {
        if (tablero[0][0] == 'X' && tablero[1][1] == 'X' && tablero[2][2] == 'X' || tablero[0][2] == 'X' && tablero[1][1] == 'X' && tablero[2][0] == 'X') {
            solucion = 'X';
        } else if (tablero[0][0] == 'O' && tablero[1][1] == 'O' && tablero[2][2] == 'O' || tablero[0][2] == 'O' && tablero[1][1] == 'O' && tablero[2][0] == 'O') {
            solucion = 'O';
        }
    }
    if(solucion!='X'&&solucion!='O')
    {
        for(int i=0;i<3;i++)
        {
            for(int j=0;j<3;j++)
            {
                if(tablero[i][j]==' ')
                {
                    solucion='_';
                }

            }
        }
    }
    return solucion;
}