DJ Example in UAV Context

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DJ Examplein UAV Context

• Karl Lieberherr

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Frame Structure
Frame
X1
X2
X3
X4
X5
A
X6
X7
B
X8
Annotation
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Frame Traversal Strategy
from Frame through A,B to Annotation
Frame
X1
X2
X3
X4
X5
A
X6
X7
B
X8
Annotation
4
Selected Paths
from Frame through A,B to Annotation
Frame
X1
X2
X3
X4
X5
A
X6
X7
B
X8
Annotation
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DJ Program

• class Frame
• public updateAnnotations()
• List annotations
• Main.cg.asList(this,
• from Frame through A,B to
  Annotation)
• Iterator it annotations.iterator()
• while (it.hasNext())
• Annotation a (Annotation) it.next()
• // use set on iterator to
• // replace Annotation object

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asList

• Adapts a traversal to the Java Collections
  Framework as a List object.
• Lazy traversal.
• Crosscutting lists they cut across an object.
• Can go forward and backward and modify object in
  place.

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asList (continued)

• Implementation uses a separate Java thread as a
  coroutine.
• Modifications to the object structure while a
  traversal is paused can be seen when the
  traversal resumes.

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Conclusion

• If we add complex object structures to the UAV
  application the benefits of DJ become apparent.
• asList is only one possible method to invoke on
  a ClassGraph object.
• Alternatives traverse, fetch, gather.