Summary

Make java.awt.MultipleGradientPaint a sealed class

Problem

java.awt.MultipleGradientPaint has only two current sub-classes, and no others can be created by applications since there are no public or protected constructors, but this is not as clear as it could be.

Solution

Use the new JDK 17 sealed modifier on the MultipleGradientPaint class and enumerate the allowed extant sub-classes.

Specification

java.awt.MultipleGradientPaint

-public abstract class MultipleGradientPaint implements Paint 
+public abstract sealed class MultipleGradientPaint implements Paint
+    permits LinearGradientPaint,
+            RadialGradientPaint