From eff001491ec8e3c07254171852c29fa836cf4e1f Mon Sep 17 00:00:00 2001 From: Umesh Awasthi Date: Sun, 19 Jan 2020 20:03:54 -0800 Subject: [PATCH] How to read file in Java --- Java/java-read-file/.idea/.gitignore | 2 + Java/java-read-file/java-read-file.iml | 2 + Java/java-read-file/pom.xml | 28 ++++++ .../read/file/JavaReadFileTest.java | 29 ++++++ .../read/file/JavaReaderFiles.java | 88 +++++++++++++++++++ .../read/file/ReadDataWithJava7.java | 64 ++++++++++++++ .../read/file/ReadFileUsingJava8.java | 49 +++++++++++ .../src/main/resources/read_java_file.txt | 3 + .../src/main/resources/special_char_data.txt | 2 + .../stream_tokenizer_read_java_file.txt | 2 + 10 files changed, 269 insertions(+) create mode 100644 Java/java-read-file/.idea/.gitignore create mode 100644 Java/java-read-file/java-read-file.iml create mode 100644 Java/java-read-file/pom.xml create mode 100644 Java/java-read-file/src/main/java/com/javadevjournal/read/file/JavaReadFileTest.java create mode 100644 Java/java-read-file/src/main/java/com/javadevjournal/read/file/JavaReaderFiles.java create mode 100644 Java/java-read-file/src/main/java/com/javadevjournal/read/file/ReadDataWithJava7.java create mode 100644 Java/java-read-file/src/main/java/com/javadevjournal/read/file/ReadFileUsingJava8.java create mode 100644 Java/java-read-file/src/main/resources/read_java_file.txt create mode 100644 Java/java-read-file/src/main/resources/special_char_data.txt create mode 100644 Java/java-read-file/src/main/resources/stream_tokenizer_read_java_file.txt diff --git a/Java/java-read-file/.idea/.gitignore b/Java/java-read-file/.idea/.gitignore new file mode 100644 index 0000000..e7e9d11 --- /dev/null +++ b/Java/java-read-file/.idea/.gitignore @@ -0,0 +1,2 @@ +# Default ignored files +/workspace.xml diff --git a/Java/java-read-file/java-read-file.iml b/Java/java-read-file/java-read-file.iml new file mode 100644 index 0000000..78b2cc5 --- /dev/null +++ b/Java/java-read-file/java-read-file.iml @@ -0,0 +1,2 @@ + + \ No newline at end of file diff --git a/Java/java-read-file/pom.xml b/Java/java-read-file/pom.xml new file mode 100644 index 0000000..e55edf8 --- /dev/null +++ b/Java/java-read-file/pom.xml @@ -0,0 +1,28 @@ + + + 4.0.0 + + com.javadevjournal + java-read-file + 1.0-SNAPSHOT + + + 1.8 + 1.8 + + + + + + org.apache.maven.plugins + maven-compiler-plugin + + 1.8 + 1.8 + + + + + \ No newline at end of file diff --git a/Java/java-read-file/src/main/java/com/javadevjournal/read/file/JavaReadFileTest.java b/Java/java-read-file/src/main/java/com/javadevjournal/read/file/JavaReadFileTest.java new file mode 100644 index 0000000..a04aa80 --- /dev/null +++ b/Java/java-read-file/src/main/java/com/javadevjournal/read/file/JavaReadFileTest.java @@ -0,0 +1,29 @@ +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(); + } +} diff --git a/Java/java-read-file/src/main/java/com/javadevjournal/read/file/JavaReaderFiles.java b/Java/java-read-file/src/main/java/com/javadevjournal/read/file/JavaReaderFiles.java new file mode 100644 index 0000000..c3556df --- /dev/null +++ b/Java/java-read-file/src/main/java/com/javadevjournal/read/file/JavaReaderFiles.java @@ -0,0 +1,88 @@ +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(); + } +} diff --git a/Java/java-read-file/src/main/java/com/javadevjournal/read/file/ReadDataWithJava7.java b/Java/java-read-file/src/main/java/com/javadevjournal/read/file/ReadDataWithJava7.java new file mode 100644 index 0000000..3e586c7 --- /dev/null +++ b/Java/java-read-file/src/main/java/com/javadevjournal/read/file/ReadDataWithJava7.java @@ -0,0 +1,64 @@ +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(); + } +} diff --git a/Java/java-read-file/src/main/java/com/javadevjournal/read/file/ReadFileUsingJava8.java b/Java/java-read-file/src/main/java/com/javadevjournal/read/file/ReadFileUsingJava8.java new file mode 100644 index 0000000..c8fb469 --- /dev/null +++ b/Java/java-read-file/src/main/java/com/javadevjournal/read/file/ReadFileUsingJava8.java @@ -0,0 +1,49 @@ +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 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 stream = Files.lines(path)){ + // read one line ar a time + stream.forEach(s-> sb.append(s).append("/n")); + } + + System.out.println(sb.toString()); + } +} diff --git a/Java/java-read-file/src/main/resources/read_java_file.txt b/Java/java-read-file/src/main/resources/read_java_file.txt new file mode 100644 index 0000000..e992266 --- /dev/null +++ b/Java/java-read-file/src/main/resources/read_java_file.txt @@ -0,0 +1,3 @@ +This file contains data to test +the different ways to read file in +Java. \ No newline at end of file diff --git a/Java/java-read-file/src/main/resources/special_char_data.txt b/Java/java-read-file/src/main/resources/special_char_data.txt new file mode 100644 index 0000000..17e86e2 --- /dev/null +++ b/Java/java-read-file/src/main/resources/special_char_data.txt @@ -0,0 +1,2 @@ +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 \ No newline at end of file diff --git a/Java/java-read-file/src/main/resources/stream_tokenizer_read_java_file.txt b/Java/java-read-file/src/main/resources/stream_tokenizer_read_java_file.txt new file mode 100644 index 0000000..d956610 --- /dev/null +++ b/Java/java-read-file/src/main/resources/stream_tokenizer_read_java_file.txt @@ -0,0 +1,2 @@ +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. \ No newline at end of file