quoting originally filed 6784594:
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http://download.oracle.com/javase/6/docs/api/java/awt/Color.html#brighter()
http://download.oracle.com/javase/6/docs/api/java/awt/Color.html#darker()

Java SE specification states for java.awt.Color.brighter()/darker() methods:

For instance "darker"
  "This method applies an arbitrary scale factor to each of the three RGB 
   components of this Color to create a darker version of this Color."

This means that alpha component must remain unchanged, however it is not
the case for many Java implementations: 1.4.2, 5.0, 6.0, 7.
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The following code illustrates that alpha is being reset to 255.


import java.awt.*;

public class ColorBrighterDarker {
    
    public static void main(String[] args) {
        System.out.println(new Color(123, 123, 123, 123).brighter().getAlpha());
        System.out.println(new Color(123, 123, 123, 123).darker().getAlpha());
    }

}
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The output will be

255
255