java 간단한 파일 입출력 질문

import java.io.FileOutputStream;
import java.io.FileInputStream;
import java.io.ObjectOutputStream;
import java.io.ObjectInputStream;
import java.io.IOException;
import java.io.Serializable;
 
 
public class Point implements Serializable{
	private double x;
	private double y;
 
	public Point(double x, double y) {
		this.x = x;
		this.y = y;
	}
 
	public void setX(double x) {
		this.x = x;
	}
 
	public void setY(double y) {
		this.y = y;
	}
 
	public double getX() {
		return x;
	}
 
	public double getY() {
		return y;
	}
 
	public static Point loadPoint(String fileName) {
		ObjectInputStream inputStream = null;
		try {
			inputStream = new ObjectInputStream(new FileInputStream(fileName));			
		}
		catch(IOException e) {
			System.out.println("Error opening input file "+fileName+".");
			System.exit(0);
		}
		Point readOne = null;
		try {
			readOne = (Point)inputStream.readObject();			
			inputStream.close();
		}
		catch (IOException e) {
			System.out.println("Error reading from file "+fileName+".");
			System.exit(0);
		}
 
		return readOne;
	}
 
	public static void savePoint(String fileName, Point pt) {
		ObjectOutputStream outputStream = null;
		try {
			outputStream = new ObjectOutputStream(new FileOutputStream (fileName));			 	
		}		
		catch (IOException e) {
			System.out.println("Error opening file " + fileName + ".");
			System.exit(0);			
		}
		try {
			outputStream.writeObject(pt);
			outputStream.close();
		}
		catch (IOException e) {
			System.out.println("Error writing to file " + fileName + ".");
			System.exit(0);			
		}
 
 
	}
 
	public double distance(Point pt) {
		return Math.sqrt(Math.pow(pt.getX() - x, 2.0) + Math.pow(pt.getY() - y, 2.0));
	}
 
	public static void main(String[] args) {		 
		 Point a = new Point(1, 2);
		 System.out.println();
	 Point.savePoint("a.pt", a);
 
		 Point.loadPoint("a.pt");
//		 System.out.println(b.getX());
	}
 
}