Home > Articles > Programming > Java

  • Print
  • + Share This
This chapter is from the book

Summary

Section 2.2 Your First Program in Java: Printing a Line of Text

  • A Java application (p. 38) executes when you use the java command to launch the JVM.
  • Comments (p. 39) document programs and improve their readability. The compiler ignores them.
  • A comment that begins with // is an end-of-line comment—it terminates at the end of the line on which it appears.
  • Traditional comments (p. 39) can be spread over several lines and are delimited by /* and */.
  • Javadoc comments (p. 39), delimited by /** and */, enable you to embed program documentation in your code. The javadoc utility program generates HTML pages based on these comments.
  • A syntax error (p. 39; also called a compiler error, compile-time error or compilation error) occurs when the compiler encounters code that violates Java's language rules. It's similar to a grammar error in a natural language.
  • Blank lines, space characters and tab characters are known as white space (p. 39). White space makes programs easier to read and is ignored by the compiler.
  • Keywords (p. 40) are reserved for use by Java and are always spelled with all lowercase letters.
  • Keyword class (p. 40) introduces a class declaration.
  • By convention, all class names in Java begin with a capital letter and capitalize the first letter of each word they include (e.g., SampleClassName).
  • A Java class name is an identifier—a series of characters consisting of letters, digits, underscores (_) and dollar signs ($) that does not begin with a digit and does not contain spaces.
  • Java is case sensitive (p. 40)—that is, uppercase and lowercase letters are distinct.
  • The body of every class declaration (p. 40) is delimited by braces, { and }.
  • A public (p. 40) class declaration must be saved in a file with the same name as the class followed by the ".java" file-name extension.
  • Method main (p. 41) is the starting point of every Java application and must begin with

    public static void main( String[] args )

    otherwise, the JVM will not execute the application.

  • Methods perform tasks and return information when they complete them. Keyword void (p. 41) indicates that a method will perform a task but return no information.
  • Statements instruct the computer to perform actions.
  • A string (p. 41) in double quotes is sometimes called a character string or a string literal.
  • The standard output object (System.out; p. 41) displays characters in the command window.
  • Method System.out.println (p. 41) displays its argument (p. 41) in the command window followed by a newline character to position the output cursor to the beginning of the next line.
  • You compile a program with the command javac. If the program contains no syntax errors, a class file (p. 43) containing the Java bytecodes that represent the application is created. These bytecodes are interpreted by the JVM when you execute the program.
  • To run an application, type java (p. 38) followed by the name of the class that contains main.

Section 2.3 Modifying Your First Java Program

  • System.out.print (p. 44) displays its argument and positions the output cursor immediately after the last character displayed.
  • A backslash (\) in a string is an escape character (p. 45). Java combines it with the next character to form an escape sequence (p. 45). The escape sequence \n (p. 45) represents the newline character.

Section 2.4 Displaying Text with printf

  • System.out.printf method (p. 46; f means "formatted") displays formatted data.
  • Method printf's first argument is a format string (p. 47) containing fixed text and/or format specifiers. Each format specifier (p. 47) indicates the type of data to output and is a placeholder for a corresponding argument that appears after the format string.
  • Format specifiers begin with a percent sign (%) and are followed by a character that represents the data type. The format specifier %s (p. 47) is a placeholder for a string.

Section 2.5 Another Application: Adding Integers

  • An import declaration (p. 48) helps the compiler locate a class that's used in a program.
  • Java's rich set of predefined classes are grouped into packages (p. 48)—named groups of classes. These are referred to as the Java class library (p. 48), or the Java Application Programming Interface (Java API).
  • A variable (p. 49) is a location in the computer's memory where a value can be stored for use later in a program. All variables must be declared with a name and a type before they can be used.
  • A variable's name enables the program to access the variable's value in memory.
  • A Scanner (package java.util; p. 49) enables a program to read data that the program will use. Before a Scanner can be used, the program must create it and specify the source of the data.
  • Variables should be initialized (p. 49) to prepare them for use in a program.
  • The expression new Scanner(System.in) creates a Scanner that reads from the standard input object (System.in; p. 49)—normally the keyboard.
  • Data type int (p. 49) is used to declare variables that will hold integer values. The range of values for an int is –2,147,483,648 to +2,147,483,647.
  • Types float and double (p. 49) specify real numbers with decimal points, such as 3.4 and –11.19.
  • Variables of type char (p. 49) represent individual characters, such as an uppercase letter (e.g., A), a digit (e.g., 7), a special character (e.g., * or %) or an escape sequence (e.g., newline, \n).
  • Types such as int, float, double and char are primitive types (p. 49). Primitive-type names are keywords; thus, they must appear in all lowercase letters.
  • A prompt (p. 50) directs the user to take a specific action.
  • Scanner method nextInt obtains an integer for use in a program.
  • The assignment operator, = (p. 51), enables the program to give a value to a variable. It's called a binary operator (p. 51) because it has two operands.
  • Portions of statements that have values are called expressions (p. 51).
  • The format specifier %d (p. 51) is a placeholder for an int value.

Section 2.6 Memory Concepts

  • Variable names (p. 52) correspond to locations in the computer's memory. Every variable has a name, a type, a size and a value.
  • A value that's placed in a memory location replaces the location's previous value, which is lost.

Section 2.7 Arithmetic

  • The arithmetic operators (p. 53) are + (addition), - (subtraction), * (multiplication), / (division) and % (remainder).
  • Integer division (p. 53) yields an integer quotient.
  • The remainder operator, % (p. 53), yields the remainder after division.
  • Arithmetic expressions must be written in straight-line form (p. 54).
  • If an expression contains nested parentheses (p. 54), the innermost set is evaluated first.
  • Java applies the operators in arithmetic expressions in a precise sequence determined by the rules of operator precedence (p. 54).
  • When we say that operators are applied from left to right, we're referring to their associativity (p. 54). Some operators associate from right to left.
  • Redundant parentheses (p. 56) can make an expression clearer.

Section 2.8 Decision Making: Equality and Relational Operators

  • The if statement (p. 56) makes a decision based on a condition's value (true or false).
  • Conditions in if statements can be formed by using the equality (== and !=) and relational (>, <, >= and <=) operators (p. 56).
  • An if statement begins with keyword if followed by a condition in parentheses and expects one statement in its body.
  • The empty statement (p. 59) is a statement that does not perform a task.
  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020