Zdiv's Software Snippet: [Java] File Read Examples (File to String and InputStream to String)

1. File Read line by line

1) Read Line with BufferedReader (JDK1.1) Example

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class FileReadLineBr {
    public static void main(String[] args) {
        String fileName = "d:/source.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();
        }
    }
}

2) Read Line with Scanner (JDK1.5) Example

import java.io.File;
import java.io.IOException;
import java.util.Scanner;

public class FileReadLineScanner {
    public static void main(String[] args) {
        String fileName = "d:/source.txt";
        try {
            Scanner scanner = new Scanner(new File(fileName));
            while (scanner.hasNext()) {
                System.out.println(scanner.nextLine());
            }
        } catch (IOException e) {
                e.printStackTrace();
        }
    }
}

3) Read Line with readAllLines (JDK1.7) Example

import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;

public class FileReadLineAllBytes {
    public static void main(String[] args) {
        String fileName = "d:/source.txt";
        try {
            List<String> lines = Files.readAllLines(Paths.get(fileName), Charset.defaultCharset());
            lines.forEach(System.out::println);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

4) Read Line with BufferedReader + Stream (JDK1.8) Example

import java.io.BufferedReader;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;

public class FileReadLineStreamBr {
    public static void main(String[] args) {
        String fileName = "d:/source.txt";
        try {
            BufferedReader br = Files.newBufferedReader(Paths.get(fileName));
            List<String> list = br.lines().collect(Collectors.toList());
            list.forEach(System.out::println);
        } catch (IOException e) {
            e.printStackTrace();
        }    
    }
}

5) Read Line with Stream (JDK1.8) Example

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class FileReadLineStream {
    public static void main(String[] args) {
        String fileName = "d:/source.txt";
        try {
            Stream<String> stream = Files.lines(Paths.get(fileName));
            List<String> list = stream
                        .filter(line -> !line.contains("public"))
                        .map(String::toUpperCase)
                        .collect(Collectors.toList());
            list.forEach(System.out::println);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

2. File Read to String

1) Read to String with readAllBytes Example

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;

public class FileReadToStringAllBytes {
    public static void main(String[] args) {
        String fileName = "d:/source.txt";
        try {
            byte[] b = Files.readAllBytes(Paths.get(fileName));
            String s = new String(b, StandardCharsets.UTF_8);
            System.out.println(s);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

2) Read to String with Scanner Example

import java.io.File;
import java.io.IOException;
import java.util.Scanner;

public class FileReadToStringScanner {
    public static void main(String[] args) {
        String fileName = "d:/source.txt";
        try {
            Scanner scanner = new Scanner( new File(fileName), "UTF-8" );
            String s = scanner.useDelimiter("\\A").next();
            scanner.close(); // Put this call in a finally block
            System.out.println(s);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

3. InputStream to String

1) InputStream read() to ByteArrayOutputStream Example

public static String InputStreamToStringByRead(InputStream is) { //1343
    try {
        ByteArrayOutputStream result = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int length;
        while ((length = is.read(buffer)) != -1) {
            result.write(buffer, 0, length);
        }
        return result.toString("UTF-8");
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

2) InputStreamReader read() to StringBuilder Example

public static String InputStreamToStringByStringBuilder1(InputStream is) { //6980
    final int bufferSize = 1024;
    final char[] buffer = new char[bufferSize];
    final StringBuilder out = new StringBuilder();
    Reader in = null;
    try {
        in = new InputStreamReader(is, "UTF-8");
        for (; ; ) {
            int rsz = in.read(buffer, 0, buffer.length);
            if (rsz < 0) {
                break;
            }
            out.append(buffer, 0, rsz);
        }
        return out.toString();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

3) InputStream read() to StringBuilder Example

public static String InputStreamToStringByStringBuilder(InputStream is) { //8977
    try {
        int ch;
        StringBuilder sb = new StringBuilder();
        while((ch = is.read()) != -1) {
            sb.append((char) ch);
        }
        is.reset();
        return sb.toString();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

4) InputStream Scanner Example

public static String InputStreamToStringByScanner(InputStream is) {
    Scanner s = new Scanner(is).useDelimiter("\\A");
    return s.hasNext() ? s.next() : "";
}

5) BufferedInputStream read() to ByteArrayOutputStream Example

public static String InputStreamToStringByByteArray(InputStream is) {
    BufferedInputStream bis = new BufferedInputStream(is);
    ByteArrayOutputStream buf = new ByteArrayOutputStream();
    int result = 0;
    try {
        result = bis.read();
        while(result != -1) {
            buf.write((byte) result);
            result = bis.read();
        }
        return buf.toString("UTF-8");
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

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2018년 3월 14일 수요일

[Java] File Read Examples (File to String and InputStream to String)

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