1 / 23

COMP206-08S General Programming 2

COMP206-08S General Programming 2. Course Goals. First three weeks: To learn about Java programming To learn about data structures – in particular, learning how to use those provided with Java (in libraries) Second three weeks: To learn about Polymorphism

meryle
Download Presentation

COMP206-08S General Programming 2

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. COMP206-08SGeneral Programming 2

  2. Course Goals First three weeks: • To learn about Java programming • To learn about data structures – in particular, learning how to use those provided with Java (in libraries) Second three weeks: • To learn about Polymorphism • To learn about Java GUI programming (Swing) • To learn more about Java libraries such as FileIO and streams Department of Computer Science

  3. Java programming language • Developed by Sun in the early 1990s • Object-oriented: programs consist of objects that interact with each other • Platform-independent: programs can run on many operating systems • Java code is translated to byte code, which is executed by a JVM • Similar to C# Department of Computer Science

  4. Course Outline • Lectures (Mon, Wed, Fri) • Labs every day – supervised 10-11 • Assessment = 6 weekly assignments + 2 tests Department of Computer Science

  5. Data Structures • A way of organizing data so that certain operations can be performed efficiently • Data structures are generic (ideally) • Examples (linked lists, stacks, queues, trees, hash tables, heaps) • Many of these are implemented in Java’s Collection Framework Department of Computer Science

  6. IDEs • Most programming languages have integrated development environments • For Java we will use Eclipse • For instructions on how to set up Eclipse please see the 203 homepage at http://www.cs.waikato.ac.nz/~eibe/COMP203A/ • Note that you can use Version 5 or Version 6 of Java – the book is based on Version 5 and Version 6 is the latest. Department of Computer Science

  7. Java – summary of syntax • Comments • One-line use: • // This is a comment • Multi-line use: • /* This is a bit longer */ • Javadoc • /** Automatic documentation! */ Department of Computer Science

  8. Types Primitive types and constants: byte aByte = 12; // -128 to 127 short aShort = 354; // -32,768 to 32,767 int anInt = 55677; // +- 2 billion long aLong = 12345678900; // +-2 power 63 float aFloat = 32.1f; // 32-bit floating point 6 sdig double aDouble = 26.5; // 64-bit 15 sig digits char aChar = ‘b’; // Unicode 30,000 chars! boolean aBool = true; Department of Computer Science

  9. Compiling Java code • The command javac file.java compiles source code and creates bytecode • Source code is stored in .java files • Bytecode is stored in .class files • The command java starts the Java Virtual Machine (JVM) and executes the bytecode • The bytecode is translated into machine-code • Most JVMs are just-in-time compilers Department of Computer Science

  10. Useful methods • When the bytecode for a .java file is executed, the main method is called: public static void main (String[ ] args) { } • This is the starting point of a Java program • To get output from your program you can write to the standard output stream using the println method System.out.println(“Hello World”); Department of Computer Science

  11. Basic Operators • Assignment operators: • +, +=, -=, *=, /= • Binary arithmetic operators: • +, - , *, /, % (remainder) • Unary operators: • -, ++, -- • Type conversion operators: • int x = 6; int y = 10; • double q = (double) x / y; Department of Computer Science

  12. Conditional statements • Equality operators: • ==, != • Relational operators: • <, <=, >, >= • Logical operators: • &&, ||, ! • The if statement if (expression) statement next statement Department of Computer Science

  13. Conditionals continued • The switch statement can be used when several options are needed • Break statement exits from the innermost loop or switch statement • Continue statement goes to the next iteration of the innermost loop immediately (ie avoiding the statements of the loop) • Conditional operator • testExpr ? yesExpr : noExpr Department of Computer Science

  14. Methods • Methods can be overloaded: a class can have multiple methods with the same name (but different parameter lists) • Public methods are visible in other classes • Static methods are not bound to a particular object Department of Computer Science

  15. Loops • The for statement: • for (initialisation; test; update) statement next statement • The while statement: • while(expression) statement next statement • The do statement: • do statement while (expression); next statement Department of Computer Science

  16. Methods • Basic method header has a name, return type and parameter list • The method declaration includes the body • Arguments are copied into the parameters: so Java is pass by value • The return statement is used to return a value to the caller • return must be present unless method is void Department of Computer Science

  17. Reference types • All types that are not primitive types are reference types • A reference variable holds the address of an object • References can be compared using == and != • This checks whether two variables refer to exactly the same object (ie they hold the same address) • References have the value null if they do not refer to an object. Department of Computer Science

  18. Objects • An instance of any of the non-primitive types is an object • The keyword new is used to invoke the constructor of an object • The dot operator is used to access an object via a reference variable • Objects are garbage-collected when they are no longer referenced by any variable Department of Computer Science

  19. Arrays • Indexed from 0 • The [ ] operator is used to index an array • An array behaves like an object • new is used to create a new array • An array variable is a reference to an array • Multi-dimensional • Dynamic arrays achieved via the ArrayList Department of Computer Science

  20. Exception handling • Handling exceptional circumstances incl errors • A try block encloses code that might generate an exception • A catch block processes the exception • A finally block maybe used which is always executed • Used for runtime (array bounds, null pointer etc), checked (IO, file not found) and errors • Exceptions are thrown Department of Computer Science

  21. Strings • Objects with special properties: • Immutable – cannot change once constructed • Can be concatenated using + • To check equality use the equals method • Many other useful methods (check the Javadoc) Department of Computer Science

  22. I/O in Java • The java.io package contains methods for input and output • Packages are made available in your class using an import statement • java.lang does not need an import statement • Java I/O is based on streams • Predefined streams include System.out, System.in and Sytem.err Department of Computer Science

  23. Examples • To read lines of input from the terminal • Create an InputStreamReader from System.in • Create a BufferedReader from the InputStreamReader • Call the readLine method on the BufferedReader • To split up a line (string) into sub strings use a StringTokenizer • For file I/O you can use a FileReader and a FileWriter Department of Computer Science

More Related