How can I create a Java program that creates license plate objects and then reads and writes them?

Here is the problem in full:
"      Write a class named CarPlate encapsulating the concept of a car license plate, assuming that it has the following attributes: the plate number, the state, and its color. Also it has the following methods: two constructors, toString(), equals(), accessors, and mutators.

"      Write a client program that creates three CarPlate objects, writes them to a file as objects, then reads them from the file as objects, outputs a description of each of the objects using the toString() method , and outputs the number of objects. When reading the objects, you should assume that you do not know the number of objects in the file.

I have done this so far.  And it works, but isn't exactly done the way that my problem asks.  Also, I can't get the program to count the number of entries.  I tried using count, but can't make it work.

public class CarPlate {
 
    private String plateLetter;
    private String plateNumber;
    private String plateState;
    private String plateColor;
    private int plateTotal;
    private int count;
 
 
 
    public CarPlate()
    {
        plateLetter="";
        plateNumber="";
        plateState="";
        plateColor="";
        count=0;
    }
    public CarPlate(String let, String num, String state, String color)
    {
        setPlate(let, num, state, color);
 
    }
    public String toString()
    {
 
        return ("Plate number "+plateLetter+" "+plateNumber+ " is a "
                +plateState+" " + " plate that is "+plateColor+" in color.");
        
 
    }
    public String equals()
    {
 
       return plateColor;
    }
    public void setPlate(String let, String num, String state, String color)
    {
        plateLetter=let;
        plateNumber=num;
        plateState=state;
        plateColor=color;
        
    }
    public String getPlateLetter(String let)
    {
        return plateLetter;
    }
    public String getPlateNumber(String num)
    {
       return plateNumber;
    }
    public String getPlateState(String state)
    {
        return plateState;
    }
    public String getPlateColor(String color)
    {
        return plateColor;
    }
 
}
 
//The following is the class to test the program
 
public class CarPlateClient {
 
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        CarPlate plate= new CarPlate();
        CarPlate plate1=new CarPlate();
        CarPlate plate2=new CarPlate();
 
        
 
        plate.setPlate("YEN", "768", "Minnesota", "blue");
        System.out.println(plate);
        
 
        plate1.setPlate("RQY", "834", "North Dakota", "brown");
        System.out.println(plate1);
 
        plate2.setPlate("OND", "012", "Wisconsin", "orange");
        System.out.println(plate2);
        
    }
 
}

Select allOpen in new window