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If the additional characters cause the size of the StringBuffer to grow beyond its current capacity when characters are added, additional memory is automatically allocated.
However, memory allocation is a relatively expensive operation and you can make your code more efficient by initializing StringBuffer capacity to a reasonable first guess. This will minimize the number of timesmemory must be allocated for it.
When using the insert methods of the StringBuffer class, you specify the index before which you want the data inserted.
Frequently you will need to convert an object to a String object because you need to pass it to a method that accepts only String values (or perhaps for some other reason) .
All classes inherit the toString method from the Object class. Many of the classes override this method to provide an implementation that is meaningful for objects of that class.
In addition, you may sometimes need to override the toString method for classes that you define to provide a meaningful toString behavior for objects of that class.
I explain the concept of overriding the toString method in detail in the module titled Java OOP: Polymorphism and the Object Class .
In Java, you specify literal strings between double quotes as in:
"I am a literal string of the String type." You can use literal strings anywhere you would use a String object.
You can also apply String methods directly to a literal string as in an earlier program that calls the length method on a literal string as shown below.
StringBuffer str6 = new StringBuffer(
StringBuffer named str6".length()); Because the compiler automatically creates a new String object for every literal string, you can use a literal string to initialize a String object (without use of the new operator) as in the following code fragment from a previous program :
String str1 = "THIS STRING IS NAMED str1"; The above construct is equivalent to, but more efficient than the following, which, according to The Java Tutorial by Campione and Walrath, ends up creating two String objects instead of one:
String str1 = new String("THIS STRING IS NAMED str1"); In this case, the compiler creates the first String object when it encounters the literal string, and the second one when it encounters new String() .
The plus (+) operator is overloaded so that in addition to performing the normal arithmetic operations, it can also be used to concatenate strings.
This will come as no surprise to you because we have been using code such as the following since the beginning of this group of Programming Fundamentals modules:
String cat = "cat";
System.out.println("con" + cat + "enation"); According to Campione and Walrath, Java uses StringBuffer objects behind the scenes to implement concatenation. They indicate that the above codefragment compiles to:
String cat = "cat";
System.out.println(new StringBuffer().append("con").append(cat).append("enation")); Fortunately, that takes place behind the scenes and we don't have to deal directly with the syntax.
I encourage you to copy the code from Listing 1 and Listing 2 . Compile the code and execute it. Experiment with the code,making changes, and observing the results of your changes. Make certain that you can explain why your changes behave as they do.
As you approach the end of this group of Programming Fundamentals modules, you should be preparing yourself for the more challenging ITSE 2321 OOP tracks identified below:
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.
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