Summary

If either ImageIcon.setImage(Image) or ImageIcon(Image) receives a null image as a parameter, the image should be set to null and no icon is rendered.

Problem

The ImageIcon.setImage method receives an Image object as a parameter. If it is null, the method throws NullPointerException from the loadImage method after it creates MediaTracker to track loading the image, which is unnecessary since the image is null. Similarly, the ImageIcon(Image) constructor throws NullPointerException if the Image object is null.

Solution

Set the current image to null and return early if a null image is passed to the ImageIcon(Image) constructor and the setImage(Image) method. A null image renders no icon.

Specification

javax.swing.ImageIcon

  /**
   * Creates an ImageIcon from an image object.
+  * If the image is {@code null}, no icon will be rendered.
   * If the image has a "comment" property that is a string,
  public ImageIcon (Image image) {

  /**
   * Sets the image displayed by this icon.
+  * Setting a {@code null} image means
+  * any existing icon will be removed
+  * and no icon will be rendered.
   * @param image the image
   */
  public void setImage(Image image) {