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The University of Akron Summit College. 2440: 160 Java Programming Java Fundamentals Instructor: Enoch E. Damson. Basic Java Programming Tips. Java is case-sensitive All Java programs must be stored in a file with a .java extension Comments are ignored by the compiler

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the university of akron summit college

The University of AkronSummit College

2440: 160Java Programming

Java Fundamentals

Instructor: Enoch E. Damson

basic java programming tips
Basic Java Programming Tips
  • Java is case-sensitive
  • All Java programs must be stored in a file with a .java extension
  • Comments are ignored by the compiler
  • A .java file may contain many classes, but may only have one public class

Java Fundamentals

basic java programming tips1
Basic Java Programming Tips…
  • In a .java file with a public class, the class must have the same name as the file
  • Every Java application program must have a method named main
  • For every opening brace { or parenthesis (, there must be a corresponding closing brace { or parenthesis ) in Java
  • Java statements are terminated with semicolons (;), except comments, method headers, or braces

Java Fundamentals

the java application programmer interface api
The Java Application Programmer Interface (API)
  • A standard library of prewritten classes for performing specific operations such as standard input and output
  • The classes and their methods are available to all Java programs
    • Some classes/methods are available automatically in all Java programs
    • Other classes/methods have to be “imported” into Java programs

Java Fundamentals

parts of a java application program
Parts of a Java Application Program
  • Below is a simple Java application

Java Fundamentals

parts of a java application program1
Parts of a Java Application Program…
  • The first line is a non-executable program comment
    • There are three comments used on Java and they include:
      • // Line commend
      • /* Paragraph comment */
      • /** Javadoc generated paragraph comment */

Java Fundamentals

parts of a java application program2
Parts of a Java Application Program…
  • The second line defines a class named Hello
    • Everything used within a Java program must be part of a class
    • A class can be defined using any name or identifier as long as it satisfies the following criteria:
      • A class name must begin with a letter of the alphabet (Unicodes etc), an underscore, or a dollar sign
      • A class name can contain only letters, digits, underscores, or dollar signs
      • A class name cannot be a Java programming reserved word

Java Fundamentals

parts of a java application program3
Parts of a Java Application Program…
  • In Java, standards are employed in the naming of classes to improve readability
    • This involves using uppercase letters to begin class names, and emphasizing each word put together as a class name with an uppercase letter
      • E.g., Employee, UnderGradStudent, InventoryItem, Year2000
  • It is recommended that established naming conventions be used in order for other programmers to interpret and follow a program
  • Some valid, but unconventional class names include:
    • employee, Undergradstudent, Inventory_Item, YEAR2000
  • The reserved word public in public class Hello is an access modifier that defines the circumstances under which a class can be accessed
    • public access is the most liberal type of access that allows other programs to access a class (also used to define methods, and data variables

Java Fundamentals

parts of a java application program4
Parts of a Java Application Program…
  • Lines #3 and #8 indicate the beginning and ending scopes of the class
    • Contents of all classes are enclosed in curly brackets { } which can contain any number of data items and methods

Java Fundamentals

parts of a java application program5
Parts of a Java Application Program…
  • Line #4 has the method header, public static void main (String[] args)
    • public – is the access modifier that allows public access to members of the HelloWorld class
    • static – is also a modifier that represents uniqueness (a class method) – only one main() method for the HelloWorld class will ever be stored in the computer memory
    • void – means the main() method returns no value when it is called
    • main() – all Java applications must have a main() method because that is the first method to be executed by a Java compiler, upon execution of an application
    • (String[] args) – is the argument passed to the main() method
      • String[] represents a Java class that can be used to represent a string of characters or array of string objects
      • args is the identifier used to hold any strings passed to the main() methods

Java Fundamentals

parts of a java application program6
Parts of a Java Application Program…
  • Lines #5 and #7 indicate the beginning and ending scopes of the main() method
    • Contents of all methods are enclosed in curly brackets { }

Java Fundamentals

parts of a java application program7
Parts of a Java Application Program…
  • Within the statement in line #6 has the statement:

System.out.println(“Hello World”);

    • System – a class defining the attributes of a collection of similar System objects like out, in. and err
    • Within, System.out.println(“Hello World”);,
    • out – is an object that represents the screen and several methods like println( ) are available with the out object
    • println() – is a method in Java programming that prints a line of output on the screen, and positions the cursor on the next line, and stands ready to accept any additional input
      • print() also prints a line of output on the screen, but it positions the cursor on the same line as the output, after printing the message
      • Method names are usually referenced followed by their parenthesis in order to distinguish them from variable names

Java Fundamentals

parts of a java application program8
Parts of a Java Application Program…
  • The dots (.) in the statement System.out.println(“Hello World”); are used to separate the names of the class, object, and method
  • The text “Hello World” is a literal string of characters that is meant to appear exactly as entered
    • Any literal string in Java programming appears between double quotation marks
  • The string “Hello World” appears within parenthesis because the string is an argument to a method (in this case the println() method)
    • Arguments consist of information that a method requires for performing its task

Java Fundamentals

special java characters
Special Java Characters

Java Fundamentals