How do I create a file and write to it in Java?
用Java创建和写入（文本）文件的最简单方法是什么？
Note that each of the code samples below may throw IOException . Try/catch/finally blocks have been omitted for brevity. See this tutorial for information about exception handling.
Creating a text file (note that this will overwrite the file if it already exists):
PrintWriter writer = new PrintWriter("the-file-name.txt", "UTF-8");
writer.println("The first line");
writer.println("The second line");
writer.close();
Creating a binary file (this will also overwrite the file):
byte data[] = ...
FileOutputStream out = new FileOutputStream("the-file-name");
out.write(data);
out.close();
Java 7+ users can use the Files class to write to files:
Creating a text file:
List<String> lines = Arrays.asList("The first line", "The second line");
Path file = Paths.get("the-file-name.txt");
Files.write(file, lines, Charset.forName("UTF-8"));
//Files.write(file, lines, Charset.forName("UTF-8"), StandardOpenOption.APPEND);
Creating a binary file:
byte data[] = ...
Path file = Paths.get("the-file-name");
Files.write(file, data);
//Files.write(file, data, StandardOpenOption.APPEND);
In Java 7 and up:
try (Writer writer = new BufferedWriter(new OutputStreamWriter(
new FileOutputStream("filename.txt"), "utf-8"))) {
writer.write("something");
}
There are useful utilities for that though:
Note also that you can use a FileWriter , but it uses the default encoding, which is often a bad idea - it's best to specify the encoding explicitly.
Below is the original, prior-to-Java 7 answer
Writer writer = null;
try {
writer = new BufferedWriter(new OutputStreamWriter(
new FileOutputStream("filename.txt"), "utf-8"));
writer.write("Something");
} catch (IOException ex) {
// Report
} finally {
try {writer.close();} catch (Exception ex) {/*ignore*/}
}
See also: Reading, Writing, and Creating Files (includes NIO2).
If you already have the content you want to write to the file (and not generated on the fly), the java.nio.file.Files addition in Java 7 as part of native I/O provides the simplest and most efficient way to achieve your goals.
Basically creating and writing to a file is one line only, moreover one simple method call !
The following example creates and writes to 6 different files to showcase how it can be used:
Charset utf8 = StandardCharsets.UTF_8;
List<String> lines = Arrays.asList("1st line", "2nd line");
byte[] data = {1, 2, 3, 4, 5};
try {
Files.write(Paths.get("file1.bin"), data);
Files.write(Paths.get("file2.bin"), data,
StandardOpenOption.CREATE, StandardOpenOption.APPEND);
Files.write(Paths.get("file3.txt"), "content".getBytes());
Files.write(Paths.get("file4.txt"), "content".getBytes(utf8));
Files.write(Paths.get("file5.txt"), lines, utf8);
Files.write(Paths.get("file6.txt"), lines, utf8,
StandardOpenOption.CREATE, StandardOpenOption.APPEND);
} catch (IOException e) {
e.printStackTrace();
}
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