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Memory management by thE StringBuffer Class

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.

The tostring method

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 .

Strings and the java compiler

In Java, you specify literal strings between double quotes as in:

Literal strings "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.

Using String methods with literal strings 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() .

Concatenation and the + operator

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.

Run the programs

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.

Looking ahead

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:

Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Jb0280: Java OOP: String and StringBuffer
  • File: Jb0280.htm
  • Originally published: 1997
  • Published at cnx.org: 11/25/12
Disclaimers:

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-

Questions & Answers

Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
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Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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