// Compiled from ImageViewerCanvas.java (version 1.4 : 48.0, super bit)
public class com.sun.activation.viewers.ImageViewerCanvas extends java.awt.Canvas {

  ...

  // Method descriptor #25 ()Ljava/awt/Dimension;
  // Stack: 5, Locals: 2
  public java.awt.Dimension getPreferredSize();
     0  aconst_null
     1  astore_1 [d]
     2  aload_0 [this]
     3  getfield com.sun.activation.viewers.ImageViewerCanvas.canvas_image : java.awt.Image [2]
     6  ifnonnull 26
     9  new java.awt.Dimension [5]
    12  dup
    13  sipush 200
    16  sipush 200
    19  invokespecial java.awt.Dimension(int, int) [6]
    22  astore_1 [d]
    23  goto 50
    26  new java.awt.Dimension [5]
    29  dup
    30  aload_0 [this]
    31  getfield com.sun.activation.viewers.ImageViewerCanvas.canvas_image : java.awt.Image [2]
    34  aload_0 [this]
    35  invokevirtual java.awt.Image.getWidth(java.awt.image.ImageObserver) : int [7]
    38  aload_0 [this]
    39  getfield com.sun.activation.viewers.ImageViewerCanvas.canvas_image : java.awt.Image [2]
    42  aload_0 [this]
    43  invokevirtual java.awt.Image.getHeight(java.awt.image.ImageObserver) : int [8]
    46  invokespecial java.awt.Dimension(int, int) [6]
    49  astore_1 [d]
    50  aload_1 [d]
    51  areturn
      Line numbers:
        [pc: 0, line: 59]
        [pc: 2, line: 61]
        [pc: 9, line: 63]
        [pc: 23, line: 64]
        [pc: 26, line: 66]
        [pc: 50, line: 69]
      Local variable table:
        [pc: 0, pc: 52] local: this index: 0 type: com.sun.activation.viewers.ImageViewerCanvas
        [pc: 2, pc: 52] local: d index: 1 type: java.awt.Dimension
  

  ...
}



=>

public class com.sun.activation.viewers.ImageViewerCanvas extends java.awt.Canvas {

  ...

  public java.awt.Dimension getPreferredSize() {
    Dimension d = null;
    if (this.canvas_image==null) {
      d = new Dimension(200,200);
    } else {
      d = new Dimension(this.canvas_image.getWidth(this),
                        this.canvas_image.getHeight(this));
    }
    return d;
  }

  ...


}