如何从文件内容创建Java字符串？

#1 楼

String content = Files.readString(path, StandardCharsets.US_ASCII);

static String readFile(String path, Charset encoding)
  throws IOException
{
  byte[] encoded = Files.readAllBytes(Paths.get(path));
  return new String(encoded, encoding);
}

List<String> lines = Files.readAllLines(Paths.get(path), encoding);

try (Stream<String> lines = Files.lines(path, encoding)) {
  lines.forEach(System.out::println);
}

String content = readFile("test.txt", StandardCharsets.UTF_8);

String content = readFile("test.txt", Charset.defaultCharset());

#2 楼

 import java.io.*;
import java.nio.charset.*;
import org.apache.commons.io.*;

public String readFile() throws IOException {
    File file = new File("data.txt");
    return FileUtils.readFileToString(file, StandardCharsets.UTF_8);
}
 

#3 楼

Scanner scanner = new Scanner( new File("poem.txt") );
String text = scanner.useDelimiter("\A").next();
scanner.close(); // Put this call in a finally block

Scanner scanner = new Scanner( new File("poem.txt"), "UTF-8" );
String text = scanner.useDelimiter("\A").next();
scanner.close(); // Put this call in a finally block

#4 楼

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

String content = new String(Files.readAllBytes(Paths.get("readMe.txt")), StandardCharsets.UTF_8);

#5 楼

private String readFile(String pathname) throws IOException {

    File file = new File(pathname);
    StringBuilder fileContents = new StringBuilder((int)file.length());        

    try (Scanner scanner = new Scanner(file)) {
        while(scanner.hasNextLine()) {
            fileContents.append(scanner.nextLine() + System.lineSeparator());
        }
        return fileContents.toString();
    }
}

#6 楼

#7 楼

import java.nio.file.Files;

 String readFile(String filename) {
            File f = new File(filename);
            try {
                byte[] bytes = Files.readAllBytes(f.toPath());
                return new String(bytes,"UTF-8");
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return "";
    }

#8 楼

String result = Files.lines(Paths.get("file.txt"))
                    .parallel() // for parallel processing 
                    .map(String::trim) // to change line   
                    .filter(line -> line.length() > 2) // to filter some lines by a predicate                        
                    .collect(Collectors.joining()); // to join lines

String out = String.join("\n", Files.readAllLines(Paths.get("file.txt")));

#9 楼

public static String readFile(String file, String csName)
            throws IOException {
    Charset cs = Charset.forName(csName);
    return readFile(file, cs);
}

public static String readFile(String file, Charset cs)
            throws IOException {
    // No real need to close the BufferedReader/InputStreamReader
    // as they're only wrapping the stream
    FileInputStream stream = new FileInputStream(file);
    try {
        Reader reader = new BufferedReader(new InputStreamReader(stream, cs));
        StringBuilder builder = new StringBuilder();
        char[] buffer = new char[8192];
        int read;
        while ((read = reader.read(buffer, 0, buffer.length)) > 0) {
            builder.append(buffer, 0, read);
        }
        return builder.toString();
    } finally {
        // Potential issue here: if this throws an IOException,
        // it will mask any others. Normally I'd use a utility
        // method which would log exceptions and swallow them
        stream.close();
    }        
}

#10 楼

 static Charset charset = com.google.common.base.Charsets.UTF_8;
public static String guava_ServerFile( URL url ) throws IOException {
    return Resources.toString( url, charset );
}
public static String guava_DiskFile( File file ) throws IOException {
    return Files.toString( file, charset );
}
 

 static Charset encoding = org.apache.commons.io.Charsets.UTF_8;
public static String commons_IOUtils( URL url ) throws IOException {
    java.io.InputStream in = url.openStream();
    try {
        return IOUtils.toString( in, encoding );
    } finally {
        IOUtils.closeQuietly(in);
    }
}
public static String commons_FileUtils( File file ) throws IOException {
    return FileUtils.readFileToString( file, encoding );
    /*List<String> lines = FileUtils.readLines( fileName, encoding );
    return lines.stream().collect( Collectors.joining("\n") );*/
}
 

 public static String streamURL_Buffer( URL url ) throws IOException {
    java.io.InputStream source = url.openStream();
    BufferedReader reader = new BufferedReader( new InputStreamReader( source ) );
    //List<String> lines = reader.lines().collect( Collectors.toList() );
    return reader.lines().collect( Collectors.joining( System.lineSeparator() ) );
}
public static String streamFile_Buffer( File file ) throws IOException {
    BufferedReader reader = new BufferedReader( new FileReader( file ) );
    return reader.lines().collect(Collectors.joining(System.lineSeparator()));
}
 

 static String charsetName = java.nio.charset.StandardCharsets.UTF_8.toString();
public static String streamURL_Scanner( URL url ) throws IOException {
    java.io.InputStream source = url.openStream();
    Scanner scanner = new Scanner(source, charsetName).useDelimiter("\A");
    return scanner.hasNext() ? scanner.next() : "";
}
public static String streamFile_Scanner( File file ) throws IOException {
    Scanner scanner = new Scanner(file, charsetName).useDelimiter("\A");
    return scanner.hasNext() ? scanner.next() : "";
}
 

 public static String getDiskFile_Java7( File file ) throws IOException {
    byte[] readAllBytes = java.nio.file.Files.readAllBytes(Paths.get( file.getAbsolutePath() ));
    return new String( readAllBytes );
}
 

 public static String getDiskFile_Lines( File file ) throws IOException {
    StringBuffer text = new StringBuffer();
    FileInputStream fileStream = new FileInputStream( file );
    BufferedReader br = new BufferedReader( new InputStreamReader( fileStream ) );
    for ( String line; (line = br.readLine()) != null; )
        text.append( line + System.lineSeparator() );
    return text.toString();
}
 

 public static void main(String[] args) throws IOException {
    String fileName = "E:/parametarisation.csv";
    File file = new File( fileName );

    String fileStream = commons_FileUtils( file );
            // guava_DiskFile( file );
            // streamFile_Buffer( file );
            // getDiskFile_Java7( file );
            // getDiskFile_Lines( file );
    System.out.println( " File Over Disk : \n"+ fileStream );


    try {
        String src = "https://code.jquery.com/jquery-3.2.1.js";
        URL url = new URL( src );

        String urlStream = commons_IOUtils( url );
                // guava_ServerFile( url );
                // streamURL_Scanner( url );
                // streamURL_Buffer( url );
        System.out.println( " File Over Network : \n"+ urlStream );
    } catch (MalformedURLException e) {
        e.printStackTrace();
    }
}
 

#11 楼

public static String readFileToString(File file) throws IOException

public static List<String> readLines(File file) throws IOException

#12 楼

String file = ...
Path path = Paths.get(file);
String content = Files.readString(path);
// Or readString(path, someCharset), if you need a Charset different from UTF-8

#13 楼

public static String readFileAsString(String filePath) throws IOException {
    DataInputStream dis = new DataInputStream(new FileInputStream(filePath));
    try {
        long len = new File(filePath).length();
        if (len > Integer.MAX_VALUE) throw new IOException("File "+filePath+" too large, was "+len+" bytes.");
        byte[] bytes = new byte[(int) len];
        dis.readFully(bytes);
        return new String(bytes, "UTF-8");
    } finally {
        dis.close();
    }
}

#14 楼

#15 楼

String content = new String(Files.readAllBytes(Paths.get(filename)), "UTF-8");

#16 楼

public String readStringFromFile(String filePath) throws IOException {
    String fileContent = new String(Files.readAllBytes(Paths.get(filePath)));
    return fileContent;
}

#17 楼

for(String line = reader.readLine(); line != null; line = reader.readLine()) {
    stringBuilder.append(line);
    stringBuilder.append(ls);
}

#18 楼

static String readFile(File file, String charset)
        throws IOException
{
    FileInputStream fileInputStream = new FileInputStream(file);
    byte[] buffer = new byte[fileInputStream.available()];
    int length = fileInputStream.read(buffer);
    fileInputStream.close();
    return new String(buffer, 0, length, charset);
}

#19 楼

Reader input = new FileReader();
StringWriter output = new StringWriter();
try {
  IOUtils.copy(input, output);
} finally {
  input.close();
}
String fileContents = output.toString();

#20 楼

public String readStringFromInputStream(FileInputStream fileInputStream) {
    StringBuffer stringBuffer = new StringBuffer();
    try {
        byte[] buffer;
        while (fileInputStream.available() > 0) {
            buffer = new byte[fileInputStream.available()];
            fileInputStream.read(buffer);
            stringBuffer.append(new String(buffer, "ISO-8859-1"));
        }
    } catch (FileNotFoundException e) {
    } catch (IOException e) { }
    return stringBuffer.toString();
}

#21 楼

public static String readFileContent(String filename, Charset charset) throws IOException {
    RandomAccessFile raf = null;
    try {
        raf = new RandomAccessFile(filename, "r");
        byte[] buffer = new byte[(int)raf.length()];
        raf.readFully(buffer);
        return new String(buffer, charset);
    } finally {
        closeStream(raf);
    }
} 


private static void closeStream(Closeable c) {
    if (c != null) {
        try {
            c.close();
        } catch (IOException ex) {
            // do nothing
        }
    }
}

#22 楼

 try
{
  String content = new Scanner(new File("file.txt")).useDelimiter("\Z").next();
  System.out.println(content);
}
catch(FileNotFoundException e)
{
  System.out.println("not found!");
}

#23 楼

public String readAll(String fileName) throws IOException {
    List<String> lines = Files.readAllLines(new File(fileName).toPath());
    return String.join("\n", lines.toArray(new String[lines.size()]));
}

#24 楼

public String readFile() throws IOException {
        File fileToRead = new File("file path");
        List<String> fileLines = Files.readAllLines(fileToRead.toPath());
        return StringUtils.join(fileLines, StringUtils.EMPTY);
}

#25 楼

public static String slurp (final File file)
throws IOException {
    StringBuilder result = new StringBuilder();

    BufferedReader reader = new BufferedReader(new FileReader(file));

    try {
        char[] buf = new char[1024];

        int r = 0;

        while ((r = reader.read(buf)) != -1) {
            result.append(buf, 0, r);
        }
    }
    finally {
        reader.close();
    }

    return result.toString();
}

#26 楼

private String readFile(String pathname) throws IOException {

File file = new File(pathname);
StringBuilder fileContents = new StringBuilder((int)file.length());
Scanner scanner = new Scanner(file);
String lineSeparator = System.getProperty("line.separator");

try {
    while(scanner.hasNextLine()) {        
        fileContents.append(scanner.nextLine() + lineSeparator);
    }
    return fileContents.toString();
} finally {
    scanner.close();
}
}

    private String readFile(String pathname) throws IOException {
    File file = new File(pathname);
    StringBuilder fileContents = new StringBuilder((int) file.length());
    Scanner scanner = new Scanner(new BufferedReader(new FileReader(file)));
    String lineSeparator = System.getProperty("line.separator");

    try {
        if (scanner.hasNextLine()) {
            fileContents.append(scanner.nextLine());
        }
        while (scanner.hasNextLine()) {
            fileContents.append(lineSeparator + scanner.nextLine());
        }
        return fileContents.toString();
    } finally {
        scanner.close();
    }
}

#27 楼

public String fileToString(File file, Charset charset) {
  Scanner fileReader = new Scanner(file, charset);
  fileReader.useDelimiter("\Z"); // \Z means EOF.
  String out = fileReader.next();
  fileReader.close();
  return out;
}

#28 楼

String data = IO.from(new File("data.txt")).toString();

#29 楼

public String fromFileInJar(String path) {
    try ( Scanner scanner 
            = new Scanner(getClass().getResourceAsStream(path))) {
        return scanner.useDelimiter("\A").next();
    }
}

my.jar/com/some/thing/a.txt

String myTxt = fromFileInJar("/com/com/thing/a.txt");

#30 楼

String sMessage = String.join("\n", reader.lines().collect(Collectors.toList()));