JDK 7b118+
Platform : All

Method of the class javax.swing.border.StrokeBorder

    public Insets getBorderInsets(Component c, Insets insets) {}

says:

     * Reinitializes the {@code insets} parameter
     * with this border's current insets.
     * All insets are equal to the line width of the stroke.

This assertion is unclear and not always satisfied as Insets() hold integers while line width is float.

Please see the following code sample:
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import javax.swing.*;
import javax.swing.border.StrokeBorder;
import java.awt.*;
import java.awt.image.BufferedImage;

public class GetBorderInsets {

    public static void main(String[] args) {

        float lineWidth = 1.0001f;


        StrokeBorder strokeBorder =
                new StrokeBorder(new BasicStroke(lineWidth), Color.BLACK);

        Insets insets = new Insets(0, 0, 0, 0);

        JPanel component = new JPanel();
        component.setBorder(strokeBorder);

        System.out.println("returned insets = " +
                strokeBorder.getBorderInsets(component, insets));
    }
}
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The output will be:
strokeBorder.getBorderInsets(Component, insets) = java.awt.Insets[top=2,left=2,bottom=2,right=2]

Spec has to mention the way how float values are converted to integer