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The code shown in Listing 9 calls the setToolTipText method on the reference stored in the first element in the array to modify the state of theobject to which that reference refers. Then the code calls the showArray method to display the contents of the array.
| Listing 9 . Modifying the state of an object. |
|---|
System.out.println("Modified array contents");
((JComponent)array[0]).setToolTipText("XX");
showArray(array); |
The toolTipText property value for each of the objects referred to by the remaining elements is left undisturbed.
The output produced by the code in Listing 9 is shown below:
Modified array contents
XX B1 L2 B3 B4 L5 As you can see, except for the first element, this is a match for the display of the array contents before the state of the object referred by the firstelement was modified. However, the toolTipText property for the object referred to by the first element now contains the string "XX", instead of thestring "B0" as before.
The code in Listing 10 displays the state of each of the objects referred to by the elements in the LinkedList collection.
| Listing 10 . Display the contents of the collection again. |
|---|
System.out.println("Collection contents");
showCollection(ref); |
The output produced by Listing 10 is shown below:
Collection contents
XX B1 L2 B3 B4 L5 As you can see, the state of the object referred to by the reference stored in the first element of the collection is also changed. The toolTipText property for that object now contains the string "XX" instead of "B0" as before.
It is safe to modify the contents of the array, even to replace the references in the array with references to other objects. Such a replacement hasno impact on the contents of the collection.
However, it is also possible to use the elements of the array to modify the state of the objects referred to by the elements in the collection.
If this is what you intend to do, that's great. However, if that is not what you intend to do, that may be a problem. So, the bottom line is, be careful whatyou do with the elements in the array.
I encourage you to copy the code from Listing 1 . Paste the code into your Java editor. Thencompile and execute it.
Run the program and observe the results. Experiment with the code. Make changes, run the program again, and observe the results of your changes. Make certain that youcan explain why your changes behave as they do.
In this module, I taught you how to use the simpler version of the overloaded toArray method, declared in the Collection interface, to copy the elements from a collection into an array of type Object .
I also showed why you need to exercise care when using the elements stored in the array, to avoid corrupting the state of the objects referred to by theelements in the collection.
In the next module, I will teach you how to use the other, more complex version of the overloaded toArray method.
This section contains a variety of miscellaneous information.
Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.
I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.
In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freely available on cnx.org and that it was made and published withoutmy prior knowledge.
Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.
-end-
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