1 / 26

Introduction to Programming in Java

Introduction to Programming in Java. AP Computer Science A Dr. Persin. Contents. History First Java Application Data types Variables Strings Assignments Math, Boolean expressions Relational operations If statements System.exit. Very Brief History. Started in 1991 by SUN Microsystems

yetty
Télécharger la présentation

Introduction to Programming in Java

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Introduction to Programming in Java AP Computer Science A Dr. Persin www.Lnk2Lrn.com

  2. Contents • History • First Java Application • Data types • Variables • Strings • Assignments • Math, Boolean expressions • Relational operations • If statements • System.exit www.Lnk2Lrn.com

  3. Very Brief History • Started in 1991 by SUN Microsystems • Targeted at consumer electronics. Wanted reliable programming language. • Integrated into browsers • Evolved into write once run anywhere, integrates into Netscape • General purpose libraries released www.Lnk2Lrn.com

  4. Basic Definitions • Java is an object oriented language. • Object • Method • Class • Applications • Applets • Native classes • Threads • Exceptions www.Lnk2Lrn.com

  5. First Application /** *Hello World, first application, only output. */ public class hello{ public static void main (String [] args) { System.out.println(“Hello World”); } //end main }//end class www.Lnk2Lrn.com

  6. Notice: • Java is CASE SENSITIVE!! • Whitespace is ignored by compiler • Whitespace makes things easier to read…hence it affects your grade  • File name has to be the same as class name in file. • Need to import necessary class definitions www.Lnk2Lrn.com

  7. Variables • Variables: • Name • Type • Value • Naming: • May contain numbers,underscore,dollar sign, or letters • Can not start with number • Can be any length • Reserved keywords • Case sensitive www.Lnk2Lrn.com

  8. Primitive data types www.Lnk2Lrn.com

  9. Assignment • = • Example: int n; n = 10; or int n = 10; //same www.Lnk2Lrn.com

  10. Strings • Not a primitive class, its actually something called a wrapper class • To find a built in class’s method use API documentation. • String is a group of char’s • A character has single quotes • char c = ‘h’; • A String has double quotes • String s = “Hello World”; • Method length • int n = s.length; www.Lnk2Lrn.com

  11. Using Strings public class hello{ public static void main (String [] args) { String s = “Hello World”; System.out.println(s); //output simple string } //end main }//end class hello www.Lnk2Lrn.com

  12. Math • Unary int x = -9; • Regular math (+,-,*,/) int y = 3+x; • % modulo operator www.Lnk2Lrn.com

  13. Incrementing • Increment and Decrement • i++ equivalent to i = i + 1; • Can also do ++i, which uses i before incrementing it. • Decrementing: i--; www.Lnk2Lrn.com

  14. Casting int n = 40; Wrong : byte b = n; why?? Right: byte b = (byte) n; Type casting converts to target type www.Lnk2Lrn.com

  15. Casting II • Type char is stored as a number. The ASCII value of the character. • A declaration of : • char c = ‘B’;stores the value 66 in location ccan use its value by casting to inthow?? www.Lnk2Lrn.com

  16. Assignment • += • -= • *= • /= • %= www.Lnk2Lrn.com

  17. Boolean Expressions • boolean bb will be either true (1) or false (0) • Logical operations: !(not), && (and) || (or) • boolean a,b;a = true;b = false;System.out.println (“a && b is “ + (a && b)); www.Lnk2Lrn.com

  18. Relational Operators • == equality • != inequality • > greater than • < less than • >= greater than or equal to • <= less than or equal to www.Lnk2Lrn.com

  19. if ( x < y) { x = y; } if ( x < y ) { x = y;}else { x = 88;} The if - branching statement www.Lnk2Lrn.com

  20. If/Else • if (logic condition) {something}else if (logic condition) { something}else {something else} www.Lnk2Lrn.com

  21. Nested IF if ( x < 0 ) {System.out.println( “ x is negative “ );} else {if ( x > 0 ) { System.out.println ( “x is positive” );}//end if x > 0else {System.out.println ( “x is zero “ );} } //end else x >=0 www.Lnk2Lrn.com

  22. Switch/Case • Switch(variable){ case(1): something; break; case(23): something; break; default: something; } www.Lnk2Lrn.com

  23. Exceptions • Java exception object. • java.io.Exception most general one.Some exception like in Throwable class define methods to get the message. www.Lnk2Lrn.com

  24. try….catch blocks. • Try {…….} catch ( IOException v) {……….} www.Lnk2Lrn.com

  25. System.out.println • println is a method in the Printstream class. • Defined: • public void println(String x)can be any type of string or combination string using addition to join parts.Example: println(“hello “ + “world “ + x); www.Lnk2Lrn.com

  26. System.exit() • One method in java.lang.System • Defined: public static void exit ( int status) • Terminates currently running Java VM • Status is status code, non zero will usually mean something abnormal. • Used at end to indicate success, or in middle to signal problems. • For more practice go to http://www.javabat.com www.Lnk2Lrn.com

More Related