Basic I/O Classes Streams Files Exceptions Java</title

Contents ,[object Object],[object Object],[object Object],[object Object]

What Is Stream? Streams Basics

What is Stream? ,[object Object],[object Object],Input stream Output stream

Stream Basics ,[object Object],[object Object],[object Object],[object Object],[object Object]

Reading Text Files Using the Scanner Class

The Scanner Class ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Using Scanner for reading a Text File ,[object Object],[object Object],[object Object],[object Object],File file = new File("test.txt"); Scanner fileInput = new Scanner(file, "windows-1251"); //Read file here... fileInput.close(); Specifies the text encoding.

Reading a Text File Line by Line ,[object Object],File file = new File("somefile.txt"); //Next line may throw exception! Scanner fileInput = new Scanner(file); int lineNumber = 0; while (fileInput.hasNextLine()) { lineNumber++; System.out.printf("Line %d: %s%n", lineNumber, fileInput.nextLine()); } fileInput.close();

Writing Text Files Using the PrintStream Class

The PrintStream Class ,[object Object],[object Object],[object Object],[object Object],PrintStream fileOutput = new PrintStream ( "test.txt", "windows-1251");

Writing to a Text File ,[object Object],//Next line may throw exception PrintStream fileOutput = new PrintStream("numbers.txt"); for (int number = 1; number <= 20; number++) { fileOutput.println(number); } fileOutput.close();

Handling I/O Exceptions Introduction

What is Exception? ,[object Object],[object Object],[object Object],[object Object],[object Object]

How to Handle and Catch Exceptions? ,[object Object],[object Object],try { // Some exception is thrown } catch (<exception type> ex) { // Exception is handled } finally { // Type functionality that must be performed // no matter if exception has occurred or not } try {...} catch (FileNotFoundException fnfe) { System.out.println("Can not find file."); }

Handling Exceptions When Opening a File String fileName = "somefile.txt"; Scanner fileInput = null; try { fileInput = new Scanner(new File(fileName)); System.out.printf( "File %f successfully opened.%n", fileName); } catch (NullPointerException npe) { System.err.printf( "Can not find file %s.", fileName); } catch (FileNotFoundException fnf) { System.err.printf( "Can not find file %s.", fileName); }

Handling I/O Exceptions Live Demo

Reading and Writing Text Files More Examples

Reading and Writing Text Files – Example ,[object Object],Scanner fileInput = new Scanner( new File( " somefile .txt) ) ; int count = 0; while (fileInput.hasNext()){ String line = fileInput. next Line(); int index = line.indexOf("foundme", 0) + 1; while (index != 0) { count++; index = line.indexOf("foundme", index) + 1; } } System.out.println(count); What is missing in this code?

Fixing Subtitles – Example ,[object Object],Scanner fileInput = null; PrintStream fileOutput = null; try { // Create scanner with the Cyrillic encoding fileInput = new Scanner(new File("source.sub"), "windows-1251"); // Create PrintWriter with the Cyrillic encoding fileOutput = new PrintStream( "fixed.sub", "windows-1251"); String line; while (fileInput.hasNextLine()) { line = fileInput.nextLine(); fileOutput.println(fixLine(line)); } // Example continues…

Fixing Subtitles – Example(2) } catch (FileNotFoundException fnfe) { System.out.println(fnfe.getMessage()); } catch (UnsupportedEncodingException uee) { System.out.println(uee.getMessage()); } finally { //remember to close the streams if (null != fileInput) { fileInput.close(); } if (null != fileOutput) { fileOutput.close(); } }

Fixing Movie Subtitles Live Demo

Summary ,[object Object],[object Object],[object Object],[object Object],[object Object]

Exercises ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Exercises (2) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Exercises (3) ,[object Object],[object Object],[object Object],[object Object]

Exercises (4) ,[object Object],[object Object],[object Object],[object Object]

Exercises (5) ,[object Object],[object Object]

Basic I/O Classes Streams Files Exceptions Java</title

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