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Mit Java Dateien lesen und schreiben
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| package de.heckenmann.fileaccess; | |
| /** | |
| * http://heckenmann.de/dateien-schreiben-und-lesen/ | |
| **/ | |
| public class FileAccessTest { | |
| public static final String FILENAME = "./test.txt"; | |
| /** | |
| * TESTS. | |
| * @param a args | |
| */ | |
| public static void main(final String... a) { | |
| final FileWriterExample fwe = new FileWriterExample(); | |
| fwe.writeStringToFile(FILENAME, "Hallo Welt!"); | |
| fwe.writeByteToFile(FILENAME, "Hallo Welt!".getBytes()); | |
| final byte[] content = new FileReaderExample().readFileAsByte(FILENAME); | |
| for (final byte b : content) { | |
| System.out.print((char) b); | |
| } | |
| } | |
| } |
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| package de.heckenmann.fileaccess; | |
| import java.io.BufferedInputStream; | |
| import java.io.BufferedReader; | |
| import java.io.File; | |
| import java.io.FileInputStream; | |
| import java.io.FileReader; | |
| import java.io.IOException; | |
| public class FileReaderExample { | |
| /** | |
| * Liest den Inhalt einer Datei und gibt ihn als byte[] zurück. | |
| * !!! Dient nur zu Demozwecken. !!! | |
| * | |
| * @param filename Name / Pfad der Datei. | |
| * @return Inhalt der Datei. | |
| */ | |
| public byte[] readFileAsByte(final String filename) { | |
| final File f = new File(filename); | |
| final byte[] result = new byte[(int) f.length()]; | |
| FileInputStream fis = null; | |
| BufferedInputStream bis = null; | |
| try { | |
| // | |
| // Ab hier geschieht die eigentliche Arbeit. | |
| // | |
| fis = new FileInputStream(f); | |
| bis = new BufferedInputStream(fis); | |
| bis.read(result); // Datei einlesen. | |
| // | |
| // Hier endet die eigentliche Arbeit. | |
| // | |
| } catch (final IOException e) { | |
| e.printStackTrace(); | |
| } finally { | |
| if (fis != null) { | |
| try { | |
| fis.close(); | |
| } catch (final IOException e) { | |
| e.printStackTrace(); | |
| } | |
| } | |
| } | |
| return result; | |
| } | |
| /** | |
| * Liest den Inhalt einer Datei und gibt ihn zurück. | |
| * !!! Dient nur zu Demozwecken. !!! | |
| * | |
| * @param filename Name / Pfad der Datei. | |
| * @return Inhalt der Datei. | |
| */ | |
| public String readFileAsString(final String filename) { | |
| final File f = new File(filename); | |
| final StringBuilder result = new StringBuilder(); | |
| FileReader fr = null; | |
| BufferedReader br = null; | |
| try { | |
| // | |
| // Ab hier geschieht die eigentliche Arbeit. | |
| // | |
| fr = new FileReader(f); | |
| br = new BufferedReader(fr); | |
| for (String toAppend = br.readLine(); toAppend != null; toAppend = br.readLine()) { | |
| result.append(toAppend); // Jede Zeile wird eingelesen und zum Ergebnis hinzugefügt. | |
| } | |
| // | |
| // Hier endet die eigentliche Arbeit. | |
| // | |
| } catch (final IOException e) { | |
| e.printStackTrace(); | |
| } finally { | |
| if (fr != null) { | |
| try { | |
| fr.close(); | |
| } catch (final IOException e) { | |
| e.printStackTrace(); | |
| } | |
| } | |
| } | |
| return result.toString(); | |
| } | |
| } |
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| package de.heckenmann.fileaccess; | |
| import java.io.BufferedOutputStream; | |
| import java.io.BufferedWriter; | |
| import java.io.File; | |
| import java.io.FileNotFoundException; | |
| import java.io.FileOutputStream; | |
| import java.io.FileWriter; | |
| import java.io.IOException; | |
| public class FileWriterExample { | |
| /** | |
| * Schreibt den Inhalt vom Typ byte[] in eine Datei. | |
| * @param filename Dateiname. | |
| * @param content byte[] | |
| */ | |
| public void writeByteToFile(final String filename, final byte[] content) { | |
| final File file = new File(filename); | |
| FileOutputStream fos = null; | |
| BufferedOutputStream bos = null; | |
| try { | |
| // #################################################### | |
| fos = new FileOutputStream(file); | |
| bos = new BufferedOutputStream(fos); | |
| bos.write(content); | |
| bos.flush(); | |
| // #################################################### | |
| } catch (final FileNotFoundException e) { | |
| e.printStackTrace(); | |
| } catch (final IOException e) { | |
| e.printStackTrace(); | |
| } finally { | |
| if (fos != null) { | |
| try { | |
| fos.close(); | |
| } catch (final IOException e) { | |
| e.printStackTrace(); | |
| } | |
| } | |
| } | |
| } | |
| /** | |
| * Schreibt den String in einer Datei. | |
| * @param filename Dateiname | |
| * @param content String | |
| */ | |
| public void writeStringToFile(final String filename, final String content) { | |
| final File file = new File(filename); | |
| FileWriter fw = null; | |
| BufferedWriter bw = null; | |
| try { | |
| // #################################################### | |
| fw = new FileWriter(file); | |
| bw = new BufferedWriter(fw); | |
| bw.write(content); | |
| bw.flush(); | |
| // #################################################### | |
| } catch (final FileNotFoundException e) { | |
| e.printStackTrace(); | |
| } catch (final IOException e) { | |
| e.printStackTrace(); | |
| } finally { | |
| if (fw != null) { | |
| try { | |
| fw.close(); | |
| } catch (final IOException e) { | |
| e.printStackTrace(); | |
| } | |
| } | |
| } | |
| } | |
| } |
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