使用Java 8读取文件

package com.java.java8;

import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.stream.Stream;

/**
 * The Class ReadLargeFile.
 *
 * @author Ankit Sood Apr 20, 2017
 */
public class ReadLargeFile {

    /**
     * The main method.
     *
     * @param args
     *            the arguments
     */
    public static void main(String[] args) {
        try {
            Stream<String> stream = Files.lines(Paths.get("C:\\Users\\System\\Desktop\\demoData.txt"));
            stream.forEach(System.out::println);
        }
        catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

你可以使用Scanner类

Scanner sc=new Scanner(file);
sc.nextLine();

您需要在BufferedReader类中使用readLine()方法。 从该类创建一个新对象，并对他操作此方法，并将其保存为字符串。

BufferReader Javadoc

下面是一个完整的错误处理示例，并支持java 7之前的字符集规范。在Java 7中，您可以使用try-with-resources语法，这使得代码更简洁。

如果你只想要默认字符集，你可以跳过InputStream，使用FileReader。

InputStream ins = null; // raw byte-stream
Reader r = null; // cooked reader
BufferedReader br = null; // buffered for readLine()
try {
    String s;
    if (true) {
        String data = "#foobar\t1234\n#xyz\t5678\none\ttwo\n";
        ins = new ByteArrayInputStream(data.getBytes());
    } else {
        ins = new FileInputStream("textfile.txt");
    }
    r = new InputStreamReader(ins, "UTF-8"); // leave charset out for default
    br = new BufferedReader(r);
    while ((s = br.readLine()) != null) {
        System.out.println(s);
    }
}
catch (Exception e)
{
    System.err.println(e.getMessage()); // handle exception
}
finally {
    if (br != null) { try { br.close(); } catch(Throwable t) { /* ensure close happens */ } }
    if (r != null) { try { r.close(); } catch(Throwable t) { /* ensure close happens */ } }
    if (ins != null) { try { ins.close(); } catch(Throwable t) { /* ensure close happens */ } }
}

下面是Groovy版本，有完整的错误处理:

File f = new File("textfile.txt");
f.withReader("UTF-8") { br ->
    br.eachLine { line ->
        println line;
    }
}

在Java 7中:

String folderPath = "C:/folderOfMyFile";
Path path = Paths.get(folderPath, "myFileName.csv"); //or any text file eg.: txt, bat, etc
Charset charset = Charset.forName("UTF-8");

try (BufferedReader reader = Files.newBufferedReader(path , charset)) {
  while ((line = reader.readLine()) != null ) {
    //separate all csv fields into string array
    String[] lineVariables = line.split(","); 
  }
} catch (IOException e) {
    System.err.println(e);
}

FileReader不会让你指定编码，如果你需要指定它，使用inputstreamreader代替:

try {
    BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(filePath), "Cp1252"));         

    String line;
    while ((line = br.readLine()) != null) {
        // process the line.
    }
    br.close();

} catch (IOException e) {
    e.printStackTrace();
}

如果从Windows导入该文件，它可能具有ANSI编码(Cp1252)，因此必须指定编码。