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| 1 | +package com.rampatra.misc; |
| 2 | + |
| 3 | +import java.io.BufferedReader; |
| 4 | +import java.io.FileReader; |
| 5 | +import java.io.IOException; |
| 6 | +import java.nio.file.Files; |
| 7 | +import java.nio.file.Path; |
| 8 | +import java.nio.file.Paths; |
| 9 | +import java.util.ArrayList; |
| 10 | +import java.util.List; |
| 11 | +import java.util.stream.Collectors; |
| 12 | +import java.util.stream.Stream; |
| 13 | + |
| 14 | + |
| 15 | +/** |
| 16 | + * Various ways to read a file in Java. |
| 17 | + * |
| 18 | + * @author rampatra |
| 19 | + * @since 2019年06月03日 |
| 20 | + */ |
| 21 | +public class ReadFile { |
| 22 | + |
| 23 | + private static Stream<String> readFile(String filePath) throws IOException { |
| 24 | + return Files.lines(Paths.get(filePath)); // use Files.readAllLines() to return a List<String> instead of Stream<String> |
| 25 | + } |
| 26 | + |
| 27 | + private static String readFile(Path filePath) throws IOException { |
| 28 | + Stream<String> lines = Files.lines(filePath); |
| 29 | + String data = lines.collect(Collectors.joining("\n")); |
| 30 | + lines.close(); |
| 31 | + return data; |
| 32 | + } |
| 33 | + |
| 34 | + private static List<String> readLargeFile(Path filePath) throws IOException { |
| 35 | + try (BufferedReader reader = Files.newBufferedReader(filePath)) { |
| 36 | + List<String> result = new ArrayList<>(); |
| 37 | + for (; ; ) { |
| 38 | + String line = reader.readLine(); |
| 39 | + if (line == null) |
| 40 | + break; |
| 41 | + result.add(line); |
| 42 | + } |
| 43 | + return result; |
| 44 | + } |
| 45 | + } |
| 46 | + |
| 47 | + private static String readFileOldWay(String filePath) throws IOException { |
| 48 | + try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) { |
| 49 | + StringBuilder builder = new StringBuilder(); |
| 50 | + String currentLine = reader.readLine(); |
| 51 | + while (currentLine != null) { |
| 52 | + builder.append(currentLine); |
| 53 | + builder.append("\n"); |
| 54 | + currentLine = reader.readLine(); |
| 55 | + } |
| 56 | + // reader.close(); not required as try-with-resources is used |
| 57 | + |
| 58 | + return builder.toString(); |
| 59 | + } |
| 60 | + } |
| 61 | + |
| 62 | + public static void main(String[] args) throws IOException { |
| 63 | + readFile("src/main/java/com/rampatra/misc/reverseandadd.txt").forEach(System.out::println); |
| 64 | + System.out.println("=================="); |
| 65 | + System.out.println(readFile(Paths.get("src/main/java/com/rampatra/misc/reverseandadd.txt"))); |
| 66 | + System.out.println("=================="); |
| 67 | + System.out.println(readLargeFile(Paths.get("src/main/java/com/rampatra/misc/reverseandadd.txt"))); |
| 68 | + System.out.println("=================="); |
| 69 | + System.out.println(readFileOldWay("src/main/java/com/rampatra/misc/reverseandadd.txt")); |
| 70 | + } |
| 71 | +} |
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