Java 17 Recipes

8-1. Serializing Java Objects
 Problem
You need to serialize a class (save the contents of the class) so that you can restore it at a 
later time.
 Solution
Java implements a built-in serialization mechanism. You access that mechanism via the 
ObjectOutputStream class. In the following example, the saveSettings() method uses 
ObjectOutputStream to serialize the settings object to write the object to disk.
public class Ch_8_1_SerializeExample {
public static void main(String[] args) {
Ch_8_1_SerializeExample example = new Ch_8_1_SerializeExample();
example.start();
}
private void start() {
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ProgramSettings settings = new ProgramSettings(new Point(10,10),
new Dimension 
(300,200),
Color.blue,
"The title of the 
application" );
saveSettings(settings,"settings.bin");
ProgramSettings loadedSettings = loadSettings("settings.bin");
if(loadedSettings != null)
System.out.println("Are settings are equal? :"+loadedSettings.
equals(settings));
}
private void saveSettings(ProgramSettings settings, String filename) {
try {
FileOutputStream fos = new FileOutputStream(filename);
try (ObjectOutputStream oos = new ObjectOutputStream(fos)) {
oos.writeObject(settings);
}
} catch (IOException e) {
e.printStackTrace();
}
}
private ProgramSettings loadSettings(String filename) {
try {
FileInputStream fis = new FileInputStream(filename);
ObjectInputStream ois = new ObjectInputStream(fis);
return (ProgramSettings) ois.readObject();
} catch (IOException | ClassNotFoundException e) {
e.printStackTrace();
}
return null;
}
}
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The following is the ProgramSetting class.
package org.java17recipes.chapter08.recipe08_01;
import java.awt.*;
import java.io.Serializable;
public class ProgramSettings implements Serializable {
private static final long serialVersionUID = 1L;
private Point locationOnScreen;
private Dimension frameSize;
private Color defaultFontColor;
private String title;
// Empty constructor
public ProgramSettings() {
}
public ProgramSettings(Point locationOnScreen, Dimension frameSize, 
Color defaultFontColor, String title) {
this.locationOnScreen = locationOnScreen;
this.frameSize = frameSize;
this.defaultFontColor = defaultFontColor;
this.title = title;
}
public Point getLocationOnScreen() {
return locationOnScreen;
}
public void setLocationOnScreen(Point locationOnScreen) {
this.locationOnScreen = locationOnScreen;
}
public Dimension getFrameSize() {
return frameSize;
}
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public void setFrameSize(Dimension frameSize) {
this.frameSize = frameSize;
}
public Color getDefaultFontColor() {
return defaultFontColor;
}
public void setDefaultFontColor(Color defaultFontColor) {
this.defaultFontColor = defaultFontColor;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
ProgramSettings that = (ProgramSettings) o;
if (defaultFontColor != null ? !defaultFontColor.
equals(that.defaultFontColor) : that.defaultFontColor 
!= null)
return false;
if (frameSize != null ? !frameSize.equals(that.frameSize) : 
that.frameSize != null) return false;
if (locationOnScreen != null ? !locationOnScreen.
equals(that.locationOnScreen) : that.locationOnScreen 
!= null)
return false;
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if (title != null ? !title.equals(that.title) : that.title 
!= null) return false;
return true;
}
@Override
public int hashCode() {
int result = locationOnScreen != null ? locationOnScreen.
hashCode() : 0;
result = 31 * result + (frameSize != null ? frameSize.
hashCode() : 0);
result = 31 * result + (defaultFontColor != null ? 
defaultFontColor.hashCode() : 0);
result = 31 * result + (title != null ? title.
hashCode() : 0);
return result;
}
}