如何创建文件并用Java写入？-Java 学习之路

1204

在Java中创建和写入（文本）文件的最简单方法是什么？

30 回答

1522
Java 7值得一试：
```
Files.write(Paths.get("./output.txt"), "Information string herer".getBytes());
```
看起来很有希望......
回复于 2024-05-04T22:30:22+08:00

如果您已经拥有要写入文件的内容（而不是动态生成），那么Java 7中的java.nio.file.Files添加作为本机I / O的一部分，可以提供最简单，最有效的方法来实现您的目标 .

基本上创建和写入文件只是一行，而且 one simple method call ！

以下示例创建并写入6个不同的文件以展示如何使用它：

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();
}

回复于 2024-05-04T22:30:22+08:00

使用输入和输出流进行文件读写：

//Coded By Anurag Goel
//Reading And Writing Files
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;


public class WriteAFile {
    public static void main(String args[]) {
        try {
            byte array [] = {'1','a','2','b','5'};
            OutputStream os = new FileOutputStream("test.txt");
            for(int x=0; x < array.length ; x++) {
                os.write( array[x] ); // Writes the bytes
            }
            os.close();

            InputStream is = new FileInputStream("test.txt");
            int size = is.available();

            for(int i=0; i< size; i++) {
                System.out.print((char)is.read() + " ");
            }
            is.close();
        } catch(IOException e) {
            System.out.print("Exception");
        }
    }
}

回复于 2024-05-04T22:30:22+08:00

在Java中创建和写入文件的一种非常简单的方法：

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;

public class CreateFiles {

    public static void main(String[] args) {
        try{
            // Create new file
            String content = "This is the content to write into create file";
            String path="D:\\a\\hi.txt";
            File file = new File(path);

            // If file doesn't exists, then create it
            if (!file.exists()) {
                file.createNewFile();
            }

            FileWriter fw = new FileWriter(file.getAbsoluteFile());
            BufferedWriter bw = new BufferedWriter(fw);

            // Write in file
            bw.write(content);

            // Close connection
            bw.close();
        }
        catch(Exception e){
            System.out.println(e);
        }
    }
}

参考：File create Example in java

回复于 2024-05-04T22:30:22+08:00

119

只有一行！ path 和 line 是字符串

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

Files.write(Paths.get(path), lines.getBytes());

回复于 2024-05-04T22:30:22+08:00

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

public class FileWriterExample {
    public static void main(String [] args) {
        FileWriter fw= null;
        File file =null;
        try {
            file=new File("WriteFile.txt");
            if(!file.exists()) {
                file.createNewFile();
            }
            fw = new FileWriter(file);
            fw.write("This is an string written to a file");
            fw.flush();
            fw.close();
            System.out.println("File written Succesfully");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

回复于 2024-05-04T22:30:22+08:00

要创建文件而不覆盖现有文件：

System.out.println("Choose folder to create file");
JFileChooser c = new JFileChooser();
c.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
c.showOpenDialog(c);
c.getSelectedFile();
f = c.getSelectedFile(); // File f - global variable
String newfile = f + "\\hi.doc";//.txt or .doc or .html
File file = new File(newfile);

try {
    //System.out.println(f);
    boolean flag = file.createNewFile();

    if(flag == true) {
        JOptionPane.showMessageDialog(rootPane, "File created successfully");
    }
    else {
        JOptionPane.showMessageDialog(rootPane, "File already exists");
    }
    /* Or use exists() function as follows:
        if(file.exists() == true) {
            JOptionPane.showMessageDialog(rootPane, "File already exists");
        }
        else {
            JOptionPane.showMessageDialog(rootPane, "File created successfully");
        }
    */
}
catch(Exception e) {
    // Any exception handling method of your choice
}

回复于 2024-05-04T22:30:22+08:00

使用：

JFileChooser c = new JFileChooser();
c.showOpenDialog(c);
File writeFile = c.getSelectedFile();
String content = "Input the data here to be written to your file";

try {
    FileWriter fw = new FileWriter(writeFile);
    BufferedWriter bw = new BufferedWriter(fw);
    bw.append(content);
    bw.append("hiiiii");
    bw.close();
    fw.close();
}
catch (Exception exc) {
   System.out.println(exc);
}

回复于 2024-05-04T22:30:22+08:00

以下是使用Java创建和编写文件的一些可能方法：

Using FileOutputStream

try {
  File fout = new File("myOutFile.txt");
  FileOutputStream fos = new FileOutputStream(fout);
  BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(fos));
  bw.write("Write somthing to the file ...");
  bw.newLine();
  bw.close();
} catch (FileNotFoundException e){
  // File was not found
  e.printStackTrace();
} catch (IOException e) {
  // Problem when writing to the file
  e.printStackTrace();
}

Using FileWriter

try {
  FileWriter fw = new FileWriter("myOutFile.txt");
  fw.write("Example of content");
  fw.close();
} catch (FileNotFoundException e) {
  // File not found
  e.printStackTrace();
} catch (IOException e) {
  // Error when writing to the file
  e.printStackTrace();
}

Using PrintWriter

try {
  PrintWriter pw = new PrintWriter("myOutFile.txt");
  pw.write("Example of content");
  pw.close();
} catch (FileNotFoundException e) {
  // File not found
  e.printStackTrace();
} catch (IOException e) {
  // Error when writing to the file
  e.printStackTrace();
}

Using OutputStreamWriter

try {
  File fout = new File("myOutFile.txt");
  FileOutputStream fos = new FileOutputStream(fout);
  OutputStreamWriter osw = new OutputStreamWriter(fos);
  osw.write("Soe content ...");
  osw.close();
} catch (FileNotFoundException e) {
  // File not found
  e.printStackTrace();
} catch (IOException e) {
  // Error when writing to the file
  e.printStackTrace();
}

有关如何read and write files in Java的进一步检查本教程 .

回复于 2024-05-04T22:30:22+08:00

如果由于某种原因想要分离创建和编写的行为，那么 touch 的Java等价物就是

try {
   //create a file named "testfile.txt" in the current working directory
   File myFile = new File("testfile.txt");
   if ( myFile.createNewFile() ) {
      System.out.println("Success!");
   } else {
      System.out.println("Failure!");
   }
} catch ( IOException ioe ) { ioe.printStackTrace(); }

createNewFile() 执行存在检查并以原子方式创建文件 . 例如，如果您想在写入文件之前确保自己是文件的创建者，这将非常有用 .

回复于 2024-05-04T22:30:22+08:00

71
只需包含此套餐：
```
java.nio.file
```
然后你可以使用这段代码来编写文件：
```
Path file = ...;
byte[] buf = ...;
Files.write(file, buf);
```
回复于 2024-05-04T22:30:22+08:00

使用JFilechooser阅读与客户的集合并保存到文件 .

private void writeFile(){

    JFileChooser fileChooser = new JFileChooser(this.PATH);
    int retValue = fileChooser.showDialog(this, "Save File");

    if (retValue == JFileChooser.APPROVE_OPTION){

        try (Writer fileWrite = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(fileChooser.getSelectedFile())))){

            this.customers.forEach((c) ->{
                try{
                    fileWrite.append(c.toString()).append("\n");
                }
                catch (IOException ex){
                    ex.printStackTrace();
                }
            });
        }
        catch (IOException e){
            e.printStackTrace();
        }
    }
}

回复于 2024-05-04T22:30:22+08:00

创建示例文件：

try {
    File file = new File ("c:/new-file.txt");
    if(file.createNewFile()) {
        System.out.println("Successful created!");
    }
    else {
        System.out.println("Failed to create!");
    }
}
catch (IOException e) {
    e.printStackTrace();
}

回复于 2024-05-04T22:30:22+08:00

374
由于作者没有指定在指定它是 text (non-binary) 文件之前是否需要针对EoL _330329问题的Java版本的解决方案，因此我决定提供我的答案 .

首先，Java 6通常已达到使用寿命，并且由于作者没有指定他需要遗留兼容性，我想它自动意味着Java 7或更高版本（Java 7尚未由IBM进行EoL） . 所以，我们可以正确查看文件I / O教程：https://docs.oracle.com/javase/tutorial/essential/io/legacy.html

在Java SE 7发行版之前，java.io.File类是用于文件I / O的机制，但它有几个缺点 . 许多方法在失败时都没有抛出异常，因此无法获得有用的错误消息 . 例如，如果文件删除失败，程序将收到“删除失败”，但不知道是否因为该文件不存在，用户没有权限，或者还有其他问题 . 重命名方法不能跨平台一致地工作 . 对符号链接没有真正的支持 . 需要更多对元数据的支持，例如文件权限，文件所有者和其他安全属性 . 访问文件元数据效率低下 . 许多File方法都没有扩展 . 通过服务器请求大型目录列表可能会导致挂起 . 大目录也可能导致内存资源问题，从而导致拒绝服务 . 如果存在循环符号链接，则无法编写可递归遍历文件树的可靠代码并进行适当响应 .

哦，那排除了java.io.File . 如果无法写入/追加文件，您可能无法知道原因 .

我们可以继续查看教程：https://docs.oracle.com/javase/tutorial/essential/io/file.html#common

If you have all lines you will write (append) to the text file in advance ，推荐的方法是https://docs.oracle.com/javase/8/docs/api/java/nio/file/Files.html#write-java.nio.file.Path-java.lang.Iterable-java.nio.charset.Charset-java.nio.file.OpenOption...-

这是一个例子（简化）：
```
Path file = ...;
List<String> linesInMemory = ...;
Files.write(file, linesInMemory, StandardCharsets.UTF_8);
```
另一个例子（追加）：
```
Path file = ...;
List<String> linesInMemory = ...;
Files.write(file, linesInMemory, Charset.forName("desired charset"), StandardOpenOption.CREATE, StandardOpenOption.APPEND, StandardOpenOption.WRITE);
```
If you want to write file content as you go ：https://docs.oracle.com/javase/8/docs/api/java/nio/file/Files.html#newBufferedWriter-java.nio.file.Path-java.nio.charset.Charset-java.nio.file.OpenOption...-

简化示例（Java 8或更高版本）：
```
Path file = ...;
try (BufferedWriter writer = Files.newBufferedWriter(file)) {
    writer.append("Zero header: ").append('0').write("\r\n");
    [...]
}
```
另一个例子（追加）：
```
Path file = ...;
try (BufferedWriter writer = Files.newBufferedWriter(file, Charset.forName("desired charset"), StandardOpenOption.CREATE, StandardOpenOption.APPEND, StandardOpenOption.WRITE)) {
    writer.write("----------");
    [...]
}
```
这些方法对作者来说需要的工作量很小，在写入[text]文件时应该优先于所有其他方法 .
回复于 2024-05-04T22:30:22+08:00

best way is to use Java7: Java 7引入了一种使用文件系统的新方法，以及一个新的实用程序类 - Files . 使用Files类，我们也可以创建，移动，复制，删除文件和目录;它也可以用来读写文件 .

public void saveDataInFile(String data) throws IOException {
    Path path = Paths.get(fileName);
    byte[] strToBytes = data.getBytes();

    Files.write(path, strToBytes);
}

Write with FileChannel 如果您正在处理大文件，FileChannel可能比标准IO更快 . 以下代码使用FileChannel将String写入文件：

public void saveDataInFile(String data) 
  throws IOException {
    RandomAccessFile stream = new RandomAccessFile(fileName, "rw");
    FileChannel channel = stream.getChannel();
    byte[] strBytes = data.getBytes();
    ByteBuffer buffer = ByteBuffer.allocate(strBytes.length);
    buffer.put(strBytes);
    buffer.flip();
    channel.write(buffer);
    stream.close();
    channel.close();
}

Write with DataOutputStream

public void saveDataInFile(String data) throws IOException {
    FileOutputStream fos = new FileOutputStream(fileName);
    DataOutputStream outStream = new DataOutputStream(new BufferedOutputStream(fos));
    outStream.writeUTF(data);
    outStream.close();
}

Write with FileOutputStream

现在让我们看看如何使用FileOutputStream将二进制数据写入文件 . 以下代码转换String int bytes并使用FileOutputStream将字节写入文件：

public void saveDataInFile(String data) throws IOException {
    FileOutputStream outputStream = new FileOutputStream(fileName);
    byte[] strToBytes = data.getBytes();
    outputStream.write(strToBytes);

    outputStream.close();
}

Write with PrintWriter 我们可以使用PrintWriter将格式化文本写入文件：

public void saveDataInFile() throws IOException {
    FileWriter fileWriter = new FileWriter(fileName);
    PrintWriter printWriter = new PrintWriter(fileWriter);
    printWriter.print("Some String");
    printWriter.printf("Product name is %s and its price is %d $", "iPhone", 1000);
    printWriter.close();
}

Write with BufferedWriter: 使用BufferedWriter将String写入新文件：

public void saveDataInFile(String data) throws IOException {
    BufferedWriter writer = new BufferedWriter(new FileWriter(fileName));
    writer.write(data);

    writer.close();
}

将String附加到现有文件：

public void saveDataInFile(String data) throws IOException {
    BufferedWriter writer = new BufferedWriter(new FileWriter(fileName, true));
    writer.append(' ');
    writer.append(data);

    writer.close();
}

回复于 2024-05-04T22:30:22+08:00

public class Program {
    public static void main(String[] args) {
        String text = "Hello world";
        BufferedWriter output = null;
        try {
            File file = new File("example.txt");
            output = new BufferedWriter(new FileWriter(file));
            output.write(text);
        } catch ( IOException e ) {
            e.printStackTrace();
        } finally {
          if ( output != null ) {
            output.close();
          }
        }
    }
}

回复于 2024-05-04T22:30:22+08:00

这是一个用于创建或覆盖文件的示例程序 . 它是长版本，因此可以更容易理解 .

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;

public class writer {
    public void writing() {
        try {
            //Whatever the file path is.
            File statText = new File("E:/Java/Reference/bin/images/statsTest.txt");
            FileOutputStream is = new FileOutputStream(statText);
            OutputStreamWriter osw = new OutputStreamWriter(is);    
            Writer w = new BufferedWriter(osw);
            w.write("POTATO!!!");
            w.close();
        } catch (IOException e) {
            System.err.println("Problem writing to the file statsTest.txt");
        }
    }

    public static void main(String[]args) {
        writer write = new writer();
        write.writing();
    }
}

回复于 2024-05-04T22:30:22+08:00

您甚至可以使用 system property 创建临时文件独立于您使用的操作系统 .

File file = new File(System.*getProperty*("java.io.tmpdir") +
                     System.*getProperty*("file.separator") +
                     "YourFileName.txt");

回复于 2024-05-04T22:30:22+08:00

我认为这是最短的方式：

FileWriter fr = new FileWriter("your_file_name.txt"); // After '.' write
// your file extention (".txt" in this case)
fr.write("Things you want to write into the file"); // Warning: this will REPLACE your old file content!
fr.close();

回复于 2024-05-04T22:30:22+08:00

使用Google的Guava库，我们可以非常轻松地创建和写入文件 .

package com.zetcode.writetofileex;

import com.google.common.io.Files;
import java.io.File;
import java.io.IOException;

public class WriteToFileEx {

    public static void main(String[] args) throws IOException {

        String fileName = "fruits.txt";
        File file = new File(fileName);

        String content = "banana, orange, lemon, apple, plum";

        Files.write(content.getBytes(), file);
    }
}

该示例在项目根目录中创建一个新的 fruits.txt 文件 .

回复于 2024-05-04T22:30:22+08:00

7

如果您希望获得相对无痛苦的体验，您还可以查看Apache Commons IO package，更具体地说是FileUtils class .

永远不要忘记检查第三方库 . Joda-Time用于日期操作，Apache Commons Lang StringUtils用于常见的字符串操作，这样可以使您的代码更具可读性 .

Java是一种很棒的语言，但标准库有时候有点低级 . 虽然功能强大，但却很低级 .

回复于 2024-05-04T22:30:22+08:00

我能找到最简单的方法：

Path sampleOutputPath = Paths.get("/tmp/testfile")
try (BufferedWriter writer = Files.newBufferedWriter(sampleOutputPath)) {
    writer.write("Hello, world!");
}

它可能只适用于1.7 .

回复于 2024-05-04T22:30:22+08:00

如果我们使用Java 7及更高版本并且还知道要添加（附加）到文件的内容，我们可以在NIO包中使用newBufferedWriter方法 .

public static void main(String[] args) {
    Path FILE_PATH = Paths.get("C:/temp", "temp.txt");
    String text = "\n Welcome to Java 8";

    //Writing to the file temp.txt
    try (BufferedWriter writer = Files.newBufferedWriter(FILE_PATH, StandardCharsets.UTF_8, StandardOpenOption.APPEND)) {
        writer.write(text);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

有几点需要注意：

指定charset编码总是一个好习惯，因为我们在类 StandardCharsets 中有常量 .
该代码使用 try-with-resource 语句，其中资源在尝试后自动关闭 .

虽然OP没有问过，但是我们想要搜索具有某些特定关键字的行，例如 confidential 我们可以在Java中使用流API：

//Reading from the file the first line which contains word "confidential"
try {
    Stream<String> lines = Files.lines(FILE_PATH);
    Optional<String> containsJava = lines.filter(l->l.contains("confidential")).findFirst();
    if(containsJava.isPresent()){
        System.out.println(containsJava.get());
    }
} catch (IOException e) {
    e.printStackTrace();
}

回复于 2024-05-04T22:30:22+08:00

使用：

try (Writer writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("myFile.txt"), StandardCharsets.UTF_8))) {
    writer.write("text to write");
} 
catch (IOException ex) {
    // Handle me
}

使用 try() 将自动关闭流 . 此版本简短，快速（缓冲）并允许选择编码 .

此功能是在Java 7中引入的 .

回复于 2024-05-04T22:30:22+08:00

package fileoperations;
import java.io.File;
import java.io.IOException;

public class SimpleFile {
    public static void main(String[] args) throws IOException {
        File file =new File("text.txt");
        file.createNewFile();
        System.out.println("File is created");
        FileWriter writer = new FileWriter(file);

        // Writes the content to the file
        writer.write("Enter the text that you want to write"); 
        writer.flush();
        writer.close();
        System.out.println("Data is entered into file");
    }
}

回复于 2024-05-04T22:30:22+08:00

在Java 8中，使用文件和路径并使用try-with-resources构造 .

import java.io.BufferedWriter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

public class WriteFile{
    public static void main(String[] args) throws IOException {
        String file = "text.txt";
        System.out.println("Writing to file: " + file);
        // Files.newBufferedWriter() uses UTF-8 encoding by default
        try (BufferedWriter writer = Files.newBufferedWriter(Paths.get(file))) {
            writer.write("Java\n");
            writer.write("Python\n");
            writer.write("Clojure\n");
            writer.write("Scala\n");
            writer.write("JavaScript\n");
        } // the file will be automatically closed
    }
}

回复于 2024-05-04T22:30:22+08:00

这里我们将一个字符串输入到文本文件中：

String content = "This is the content to write into a file";
File file = new File("filename.txt");
FileWriter fw = new FileWriter(file.getAbsoluteFile());
BufferedWriter bw = new BufferedWriter(fw);
bw.write(content);
bw.close(); // Be sure to close BufferedWriter

我们可以轻松创建新文件并在其中添加内容 .

回复于 2024-05-04T22:30:22+08:00

有一些简单的方法，如：

File file = new File("filename.txt");
PrintWriter pw = new PrintWriter(file);

pw.write("The world I'm coming");
pw.close();

String write = "Hello World!";

FileWriter fw = new FileWriter(file);
BufferedWriter bw = new BufferedWriter(fw);

fw.write(write);

fw.close();

回复于 2024-05-04T22:30:22+08:00

在Java 7及更高版本中：

try (Writer writer = new BufferedWriter(new OutputStreamWriter(
              new FileOutputStream("filename.txt"), "utf-8"))) {
   writer.write("something");
}

但是有一些有用的实用程序：

989 FileUtils.writeStringtoFile(..)来自commons-io
来自 Guava

Files.write(..)

另请注意，您可以使用 FileWriter ，但它使用默认编码，这通常是一个坏主意 - 最好明确指定编码 .

以下是Java 7之前的原始答案

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*/}
}

另请参阅：Reading, Writing, and Creating Files（包括NIO2） .

回复于 2024-05-04T22:30:22+08:00

请注意，下面的每个代码示例都可能抛出 IOException . 为简洁起见，省略了try / catch / finally块 . 有关异常处理的信息，请参阅this tutorial .

创建一个文本文件（请注意，如果文件已经存在，这将覆盖该文件）：

PrintWriter writer = new PrintWriter("the-file-name.txt", "UTF-8");
writer.println("The first line");
writer.println("The second line");
writer.close();

创建二进制文件（这也会覆盖文件）：

byte data[] = ...
FileOutputStream out = new FileOutputStream("the-file-name");
out.write(data);
out.close();

Java 7+ 用户可以使用Files类写入文件：

创建文本文件：

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);

创建二进制文件：

byte data[] = ...
Path file = Paths.get("the-file-name");
Files.write(file, data);
//Files.write(file, data, StandardOpenOption.APPEND);

回复于 2024-05-04T22:30:22+08:00

如何创建文件并用Java写入？

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