Java 8 Stream - Lire un fichier ligne par ligne
Dans Java 8, vous pouvez utiliserFiles.lines pour lire le fichier en tant queStream.
c://lines.txt – A simple text file for testing
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1. Fichier de lecture Java + flux
TestReadFile.java
package com.example.java8;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.stream.Stream;
public class TestReadFile {
public static void main(String args[]) {
String fileName = "c://lines.txt";
//read file into stream, try-with-resources
try (Stream stream = Files.lines(Paths.get(fileName))) {
stream.forEach(System.out::println);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Sortie
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2. Fichier de lecture Java + Stream + Extra
Cet exemple vous montre comment utiliserStream pour filtrer le contenu, convertir tout le contenu en majuscules et le renvoyer sous forme deList.
TestReadFile2.java
package com.example.java8;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class TestReadFile2 {
public static void main(String args[]) {
String fileName = "c://lines.txt";
List list = new ArrayList<>();
try (Stream stream = Files.lines(Paths.get(fileName))) {
//1. filter line 3
//2. convert all content to upper case
//3. convert it into a List
list = stream
.filter(line -> !line.startsWith("line3"))
.map(String::toUpperCase)
.collect(Collectors.toList());
} catch (IOException e) {
e.printStackTrace();
}
list.forEach(System.out::println);
}
}
Sortie
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3. BufferedReader + Stream
Une nouvelle méthodelines() a été ajoutée depuis la 1.8, elle permet àBufferedReader de renvoyer le contenu enStream.
TestReadFile3.java
package com.example.java8;
import java.io.BufferedReader;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
public class TestReadFile3{
public static void main(String args[]) {
String fileName = "c://lines.txt";
List list = new ArrayList<>();
try (BufferedReader br = Files.newBufferedReader(Paths.get(fileName))) {
//br returns as stream and convert it into a List
list = br.lines().collect(Collectors.toList());
} catch (IOException e) {
e.printStackTrace();
}
list.forEach(System.out::println);
}
}
Sortie
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4. Classic BufferedReader And Scanner
Assez de Java 8 etStream, revisitons les exemples classiques deBufferedReader (JDK1.1) etScanner (JDK1.5) pour lire un fichier ligne par ligne, cela fonctionne toujours, seuls les développeurs se dirigent versStream.
4.1 BufferedReader + try-with-resources example.
TestReadFile4.java
package com.example.core;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class TestReadFile4{
public static void main(String args[]) {
String fileName = "c://lines.txt";
try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {
String line;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
4.2 Scanner + try-with-resources example.
TestReadFile5.java
package com.example.core;
import java.io.File;
import java.io.IOException;
import java.util.Scanner;
public class TestReadFile5 {
public static void main(String args[]) {
String fileName = "c://lines.txt";
try (Scanner scanner = new Scanner(new File(fileName))) {
while (scanner.hasNext()){
System.out.println(scanner.nextLine());
}
} catch (IOException e) {
e.printStackTrace();
}
}
}