How to read file in Java

Java/java-read-file/.idea/.gitignore

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+# Default ignored files
+/workspace.xml

Java/java-read-file/java-read-file.iml

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+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4" />

Java/java-read-file/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.javadevjournal</groupId>
+    <artifactId>java-read-file</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+    </properties>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>

Java/java-read-file/src/main/java/com/javadevjournal/read/file/JavaReadFileTest.java

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+package com.javadevjournal.read.file;
+
+import java.io.IOException;
+
+public class JavaReadFileTest {
+
+    public static void main(String[] args) throws IOException {
+
+        JavaReaderFiles readFile = new JavaReaderFiles();
+
+        // read using buffer reader
+        readFile.readFileUsingBufferReader();
+
+        //read using FileChannel
+        readFile.readFileUsingFileChannel();
+
+        //read using DataInputStream
+       readFile.readFileUsingDataInputStream();
+
+        // using scanner
+        readFile.readFileUsingScanner();
+
+        // read file using tokenizer
+        readFile.readFileStreamTokenizer();
+
+        // read file with UTF-8 data
+        readFile.readUTF8FileData();
+    }
+}

Java/java-read-file/src/main/java/com/javadevjournal/read/file/JavaReaderFiles.java

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+package com.javadevjournal.read.file;
+
+import java.io.*;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.charset.StandardCharsets;
+import java.util.Scanner;
+
+public class JavaReaderFiles {
+
+    private final String FILE_LOCATION = "src/main/resources/read_java_file.txt";
+    private final String STREAMTOKENIZER_FILE_LOCATION = "src/main/resources/stream_tokenizer_read_java_file.txt";
+    private final String UTF8_FILE_LOCATION = "src/main/resources/special_char_data.txt";
+
+    public void readFileUsingBufferReader() throws IOException {
+        BufferedReader bufferedReader = new BufferedReader(new FileReader(FILE_LOCATION));
+        String line = null;
+        while ((line = bufferedReader.readLine()) != null) {
+            // perform your logic with the data
+            System.out.println(line);
+        }
+    }
+
+    public void readFileUsingFileChannel() throws IOException {
+        RandomAccessFile file = new RandomAccessFile(FILE_LOCATION, "r");
+        FileChannel channel = file.getChannel();
+        int bufferSize = 1024;
+        ByteBuffer buffer = ByteBuffer.allocate(bufferSize);
+        while (channel.read(buffer) != -1) {
+            System.out.println(new String(buffer.array()));
+        }
+        channel.close();
+        file.close();
+    }
+
+    public void readFileUsingDataInputStream() throws IOException {
+        DataInputStream dataInputStream = new DataInputStream(new FileInputStream(FILE_LOCATION));
+        while (dataInputStream.available() > 0) {
+            System.out.println(dataInputStream.readUTF());
+        }
+    }
+
+    public void readFileUsingScanner() throws IOException {
+        Scanner scanner = new Scanner(new File(FILE_LOCATION), StandardCharsets.UTF_8.name());
+        scanner.useDelimiter("\\n");
+        while (scanner.hasNext()) {
+            // perform your logic with the data
+            System.out.println(scanner.next());
+        }
+    }
+
+    public void readFileStreamTokenizer() throws IOException {
+
+        // init the file and StreamTokenizer
+        FileReader reader = new FileReader(STREAMTOKENIZER_FILE_LOCATION);
+        StreamTokenizer tokenizer = new StreamTokenizer(reader);
+
+        // we will iterate through the output until end of file
+        while (tokenizer.nextToken() != StreamTokenizer.TT_EOF) {
+
+            // we will work on the data based on the data type
+            if(tokenizer.ttype == StreamTokenizer.TT_WORD) {
+                System.out.println(tokenizer.sval);
+            } else if(tokenizer.ttype == StreamTokenizer.TT_NUMBER) {
+                System.out.println(tokenizer.nval);
+            } else if(tokenizer.ttype == StreamTokenizer.TT_EOL) {
+                System.out.println();
+            }
+        }
+    }
+
+
+    public void readUTF8FileData() throws IOException {
+
+        // create a Buffer reader without encoding and pass encoding information
+        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream(UTF8_FILE_LOCATION)));
+        String line;
+
+        // we iterate until EOF
+        while ((line = bufferedReader.readLine()) != null) {
+            // perform your logic with the data
+            System.out.println(line);
+        }
+
+        // close the buffer
+        bufferedReader.close();
+    }
+}

Java/java-read-file/src/main/java/com/javadevjournal/read/file/ReadDataWithJava7.java

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+package com.javadevjournal.read.file;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+public class ReadDataWithJava7 {
+
+    private static final String FILE_LOCATION = "src/main/resources/read_java_file.txt";
+
+    public static void main(String[] args) {
+
+        String output = readFileReadAllBytes(FILE_LOCATION);
+        //System.out.println(output);
+
+        output = readFileBufferReader(FILE_LOCATION);
+        System.out.println(output);
+    }
+
+    /*
+       Internal method to read the data from the file using readAllBytes method
+     */
+    private static String readFileReadAllBytes(final String path){
+
+        // define a data holder to store the data read from the file
+        String data="";
+        try
+        {
+            data = new String ( Files.readAllBytes( Paths.get(path) ) );
+        }
+        catch (IOException e)
+        {
+            e.printStackTrace();
+        }
+
+        return data;
+    }
+
+    /*
+        Read files using the new Files class and BufferReader option
+     */
+    private static String readFileBufferReader(final String filePath){
+
+        // define a data holder to store the data read from the file
+       Path path = Paths.get(filePath);
+        StringBuilder fileContent = new StringBuilder();
+        try {
+
+            BufferedReader br= Files.newBufferedReader(path);
+            String line ;
+            while ((line = br.readLine()) != null) {
+                // perform your logic with the data
+                fileContent.append(line);
+            }
+        }
+        catch (IOException e)
+        {
+            e.printStackTrace();
+        }
+        return fileContent.toString();
+    }
+}

Java/java-read-file/src/main/java/com/javadevjournal/read/file/ReadFileUsingJava8.java

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+package com.javadevjournal.read.file;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.stream.Stream;
+
+public class ReadFileUsingJava8 {
+
+    private static final String FILE_LOCATION = "src/main/resources/read_java_file.txt";
+
+    public static void main(String[] args) throws IOException {
+
+        readLineByLine(FILE_LOCATION);
+        readWithBuilder(FILE_LOCATION);
+    }
+
+    /*
+     This method read the file line by line using Java 8 stream API
+     */
+    private static void readLineByLine(final String fileLocation) throws IOException {
+
+        // create the path
+        Path path = Paths.get(fileLocation);
+
+        try(Stream<String> stream = Files.lines(path)){
+            // read one line ar a time
+            stream.forEach(System.out::println);
+        }
+    }
+
+    /*
+     Read all content line by line but add them to a StringBuilder
+     */
+    private static void readWithBuilder(final String fileLocation) throws IOException {
+
+        StringBuilder sb = new StringBuilder();
+        // create the path
+        Path path = Paths.get(fileLocation);
+
+        try(Stream<String> stream = Files.lines(path)){
+            // read one line ar a time
+            stream.forEach(s-> sb.append(s).append("/n"));
+        }
+
+        System.out.println(sb.toString());
+    }
+}

Java/java-read-file/src/main/resources/read_java_file.txt

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+This file contains data to test
+the different ways to read file in
+Java.

Java/java-read-file/src/main/resources/special_char_data.txt

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+目前，美国有50个州以及1个联邦区
+在这50个州中，有48个是连续的，也就是说，它们是直接连接的

Java/java-read-file/src/main/resources/stream_tokenizer_read_java_file.txt

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+Currently, the US has 50 states as well as 1 federal district
+Of these 50 states, 48 of them are contiguous, that is, they are connected directly.