This article provides all the ways of reading file into a String in Java along with performance statistics.
Performance statistics
Below are time taken by file reading methods with 50MB file. To get fair statistics, 5 rounds of method call are counted.
| Reading method | 50 MB file read time (Milli-Seconds) |
|---|---|
| Java java.io.FileReader | 88420, 83222, 85353, 83131, 85252 |
| Java java.io.BufferedReader | 83263, 85080, 83288, 84097, 83171 |
| Java NIO java.nio.file.Files | 59, 37, 35, 36, 35 |
| Apache common-io org.apache.commons.io.FileUtils | 168, 113, 104, 145, 136 |
| Google com.google.common.io.Files | 63, 61, 58, 59, 56 |
java.io.FileReader
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/** * Read file with Java's FileReader * * @param fileToRead * @return */ public static String readWithFileReader(String fileToRead) { String readData = ""; try (FileReader fileReader = new FileReader(fileToRead)) { while (fileReader.ready()) { char[] c = new char[8192]; fileReader.read(c); readData = readData + new String(c); } } catch (IOException e) { e.printStackTrace(); } return readData; } |
java.io.BufferedReader
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/** * Read file with Java's BufferedReader * * @param fileToRead * @return */ public static String readWithBufferedReader(String fileToRead) { String readData = ""; try (FileReader fileReader = new FileReader(fileToRead); BufferedReader bufferedReader = new BufferedReader(fileReader)) { while (bufferedReader.ready()) { char[] c = new char[8192]; bufferedReader.read(c); readData = readData + new String(c); } } catch (IOException e) { e.printStackTrace(); } return readData; } |
java.nio.file.Files
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/** * Read file with Java's NIO Files * * @param fileToRead * @return */ public static String readWithNioFiles(String fileToRead) { String readData = ""; try { readData = Files.readString(Path.of(fileToRead)); } catch (IOException e) { e.printStackTrace(); } return readData; } |
org.apache.commons.io.FileUtils
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/** * Read file with Apache commons-io FileUtils */ public static String readWithApacheCommons(String fileToRead) { String readData = ""; try { readData = FileUtils.readFileToString(new File(fileToRead), "UTF-8"); } catch (IOException e) { e.printStackTrace(); } return readData; } |
com.google.common.io.Files
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/** * Read file with google guava common io Files. * * @param fileToRead * @return */ public static String readWithGoogleGuava(String fileToRead) { String readData = ""; try { readData = com.google.common.io.Files.asCharSource(new File(fileToRead), Charset.defaultCharset()).read(); } catch (IOException e) { e.printStackTrace(); } return readData; } |
Complete code with to test reading & performance
Here is the complete code which tests reading of file into Sting, print it. Also measures performance time take of all methods using Java Instant & Duration. Takes 5 readings to get fair stats.
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package com.itsallbinary.java; import java.io.BufferedReader; import java.io.File; import java.io.FileReader; import java.io.IOException; import java.nio.charset.Charset; import java.nio.file.Files; import java.nio.file.Path; import java.time.Duration; import java.time.Instant; import java.util.Arrays; import java.util.stream.Collectors; import org.apache.commons.io.FileUtils; public class WaysToReadTextFileToStringPerformance { private static final String FILE_TO_READ = "ItsAllBinary.txt"; private static final String HUGE_50MB_FILE_TO_READ = "HugeItsAllBinary.txt"; public static void main(String[] args) throws IOException { /* * Read file to String & print string. */ String readWithFileReder = readWithFileReader(FILE_TO_READ); String readWithBufferedReader = readWithBufferedReader(FILE_TO_READ); String readWithNioFiles = readWithNioFiles(FILE_TO_READ); String readWithApacheCommons = readWithApacheCommons(FILE_TO_READ); String readWithGoogleGuava = readWithGoogleGuava(FILE_TO_READ); System.out.println("Read using java.io.FileReader.read() = " + readWithFileReder); System.out.println("Read using java.io.BufferedReader.read() = " + readWithBufferedReader); System.out.println("Read using java.nio.file.Files.readString() = " + readWithNioFiles); System.out.println("Read using org.apache.commons.io.FileUtils.readFileToString() = " + readWithApacheCommons); System.out.println("Read using com.google.common.io.Files.asCharSource() = " + readWithGoogleGuava); /* * Read HUGE file & print time taken. 5 iterations will be done of each to get * fair results. */ String readWithFileRederPerf = measurePerformance(() -> readWithFileReader(HUGE_50MB_FILE_TO_READ)); String readWithBufferedReaderPerf = measurePerformance(() -> readWithBufferedReader(HUGE_50MB_FILE_TO_READ)); String readWithNioFilesPerf = measurePerformance(() -> readWithNioFiles(HUGE_50MB_FILE_TO_READ)); String readWithApacheCommonsPerf = measurePerformance(() -> readWithApacheCommons(HUGE_50MB_FILE_TO_READ)); String readWithGoogleGuavaPerf = measurePerformance(() -> readWithGoogleGuava(HUGE_50MB_FILE_TO_READ)); System.out.println("Time for java.io.FileReader.read() = " + readWithFileRederPerf); System.out.println("Time for java.io.BufferedReader() = " + readWithBufferedReaderPerf); System.out.println("Time for java.nio.file.Files.readString() = " + readWithNioFilesPerf); System.out .println("Time for org.apache.commons.io.FileUtils.readFileToString() = " + readWithApacheCommonsPerf); System.out.println("Time for com.google.common.io.Files.asCharSource() = " + readWithGoogleGuavaPerf); } /** * Measure method performance execution time using java.time.Duration & * java.time.Instant. * * @param method * @return Time taken for method in seconds or millis */ public static String measurePerformance(Runnable method) { String[] durations = new String[5]; for (int i = 0; i < 5; i++) { Instant start = Instant.now(); method.run(); Duration duration = Duration.between(start, Instant.now()); durations[i] = duration.toMillis() + " Milli-Seconds"; } return Arrays.stream(durations).collect(Collectors.joining(", ")); } /** * Read file with Java's FileReader * * @param fileToRead * @return */ public static String readWithFileReader(String fileToRead) { String readData = ""; try (FileReader fileReader = new FileReader(fileToRead)) { while (fileReader.ready()) { char[] c = new char[8192]; fileReader.read(c); readData = readData + new String(c); } } catch (IOException e) { e.printStackTrace(); } return readData; } /** * Read file with Java's BufferedReader * * @param fileToRead * @return */ public static String readWithBufferedReader(String fileToRead) { String readData = ""; try (FileReader fileReader = new FileReader(fileToRead); BufferedReader bufferedReader = new BufferedReader(fileReader)) { while (bufferedReader.ready()) { char[] c = new char[8192]; bufferedReader.read(c); readData = readData + new String(c); } } catch (IOException e) { e.printStackTrace(); } return readData; } /** * Read file with Java's NIO Files * * @param fileToRead * @return */ public static String readWithNioFiles(String fileToRead) { String readData = ""; try { readData = Files.readString(Path.of(fileToRead)); } catch (IOException e) { e.printStackTrace(); } return readData; } /** * Read file with Apache commons-io FileUtils */ public static String readWithApacheCommons(String fileToRead) { String readData = ""; try { readData = FileUtils.readFileToString(new File(fileToRead), "UTF-8"); } catch (IOException e) { e.printStackTrace(); } return readData; } /** * Read file with google guava common io Files. * * @param fileToRead * @return */ public static String readWithGoogleGuava(String fileToRead) { String readData = ""; try { readData = com.google.common.io.Files.asCharSource(new File(fileToRead), Charset.defaultCharset()).read(); } catch (IOException e) { e.printStackTrace(); } return readData; } } |
Output:
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Read using java.io.FileReader.read() = Welcome to Its All Binary ! Read using java.io.BufferedReader.read() = Welcome to Its All Binary ! Read using java.nio.file.Files.readString() = Welcome to Its All Binary ! Read using org.apache.commons.io.FileUtils.readFileToString() = Welcome to Its All Binary ! Read using com.google.common.io.Files.asCharSource() = Welcome to Its All Binary ! Time for java.io.FileReader.read() = 88420 Milli-Seconds, 83222 Milli-Seconds, 85353 Milli-Seconds, 83131 Milli-Seconds, 85252 Milli-Seconds Time for java.io.BufferedReader() = 83263 Milli-Seconds, 85080 Milli-Seconds, 83288 Milli-Seconds, 84097 Milli-Seconds, 83171 Milli-Seconds Time for java.nio.file.Files.readString() = 59 Milli-Seconds, 37 Milli-Seconds, 35 Milli-Seconds, 36 Milli-Seconds, 35 Milli-Seconds Time for org.apache.commons.io.FileUtils.readFileToString() = 168 Milli-Seconds, 113 Milli-Seconds, 104 Milli-Seconds, 145 Milli-Seconds, 136 Milli-Seconds Time for com.google.common.io.Files.asCharSource() = 63 Milli-Seconds, 61 Milli-Seconds, 58 Milli-Seconds, 59 Milli-Seconds, 56 Milli-Seconds |