在Java中,似乎有不同的方式来读取和写入文件数据。
我想从一个文件读取ASCII数据。可能的方式和它们的区别是什么?
在Java中,似乎有不同的方式来读取和写入文件数据。
我想从一个文件读取ASCII数据。可能的方式和它们的区别是什么?
当前回答
我记录了15种用Java读取文件的方法,然后测试了它们在不同文件大小下的速度——从1kb到1gb,下面是最常用的三种方法:
java.nio.file.Files.readAllBytes() Tested to work in Java 7, 8, and 9. import java.io.File; import java.io.IOException; import java.nio.file.Files; public class ReadFile_Files_ReadAllBytes { public static void main(String [] pArgs) throws IOException { String fileName = "c:\\temp\\sample-10KB.txt"; File file = new File(fileName); byte [] fileBytes = Files.readAllBytes(file.toPath()); char singleChar; for(byte b : fileBytes) { singleChar = (char) b; System.out.print(singleChar); } } } java.io.BufferedReader.readLine() Tested to work in Java 7, 8, 9. import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; public class ReadFile_BufferedReader_ReadLine { public static void main(String [] args) throws IOException { String fileName = "c:\\temp\\sample-10KB.txt"; FileReader fileReader = new FileReader(fileName); try (BufferedReader bufferedReader = new BufferedReader(fileReader)) { String line; while((line = bufferedReader.readLine()) != null) { System.out.println(line); } } } } java.nio.file.Files.lines() This was tested to work in Java 8 and 9 but won't work in Java 7 because of the lambda expression requirement. import java.io.File; import java.io.IOException; import java.nio.file.Files; import java.util.stream.Stream; public class ReadFile_Files_Lines { public static void main(String[] pArgs) throws IOException { String fileName = "c:\\temp\\sample-10KB.txt"; File file = new File(fileName); try (Stream linesStream = Files.lines(file.toPath())) { linesStream.forEach(line -> { System.out.println(line); }); } } }
其他回答
这里有一个简单的解决方案:
String content = new String(Files.readAllBytes(Paths.get("sample.txt")));
或读作列表:
List<String> content = Files.readAllLines(Paths.get("sample.txt"))
我编写的这段代码对于非常大的文件要快得多:
public String readDoc(File f) {
String text = "";
int read, N = 1024 * 1024;
char[] buffer = new char[N];
try {
FileReader fr = new FileReader(f);
BufferedReader br = new BufferedReader(fr);
while(true) {
read = br.read(buffer, 0, N);
text += new String(buffer, 0, read);
if(read < N) {
break;
}
}
} catch(Exception ex) {
ex.printStackTrace();
}
return text;
}
这基本上与Jesus Ramos的回答完全相同,除了使用File而不是FileReader加上迭代来逐级遍历文件的内容。
Scanner in = new Scanner(new File("filename.txt"));
while (in.hasNext()) { // Iterates each line in the file
String line = in.nextLine();
// Do something with line
}
in.close(); // Don't forget to close resource leaks
... 抛出FileNotFoundException
如果这是关于结构的简单性,请使用Java kiss:
import static kiss.API.*;
class App {
void run() {
String line;
try (Close in = inOpen("file.dat")) {
while ((line = readLine()) != null) {
println(line);
}
}
}
}
Cactoos提供了一个声明性的一行代码:
new TextOf(new File("a.txt")).asString();