Java 简明教程

Java - Creating Files

Create File in Java

我们可以通过多种方式在 Java 中创建一个文件。下面是最受欢迎的 3 种在 Java 中创建文件的方法 −

We can create a file in Java using multiple ways. Following are three most popular ways to create a file in Java −

Using FileOutputStream() constructor
Using File.createNewFile() method
Using Files.write() method

我们来看一看在 Java 中创建文件的每种方式。

Let’s take a look at each of the way to create file in Java.

Create File Using FileOutputStream Constructor

FileOutputStream用于创建一个文件并在其中写入数据。如果文件不存在，则流将在打开文件输出之前创建一个文件。

FileOutputStream is used to create a file and write data into it. The stream would create a file, if it doesn’t already exist, before opening it for output.

这里有 constructors，可用于创建 FileOutputStream 对象。

Here are two constructors which can be used to create a FileOutputStream object.

下面的构造函数以字符串形式获取一个文件名，用于创建一个输入流对象以写入文件：

Following constructor takes a file name as a string to create an input stream object to write the file −

Syntax

OutputStream f = new FileOutputStream("C:/java/hello.txt")

Syntax

下面的构造函数获取一个文件对象，用于创建一个输出流对象以写入文件。首先，我们使用 File() 方法创建一个文件对象，如下所示：

Following constructor takes a file object to create an output stream object to write the file. First, we create a file object using File() method as follows −

File f = new File("C:/java/hello.txt");
OutputStream f = new FileOutputStream(f);

Example: Create File Using FileOutputStream Constructor

以下是使用 FileOutputStream 在当前目录中创建文件的示例代码：

Following is the example to demonstrate FileOutputStream to create a file in current directory−

package com.tutorialspoint;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class FileTest {

   public static void main(String args[]) {

      try {
         byte bWrite [] = {65, 66, 67, 68, 69};
         OutputStream os = new FileOutputStream("test.txt");
         for(int x = 0; x < bWrite.length ; x++) {
            os.write( bWrite[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");
      }
   }
}

上述代码将创建文件 test.txt，并以二进制格式写入给定数字。stdout 屏幕上的输出也会相同。

The above code would create file test.txt and would write given numbers in binary format. Same would be the output on the stdout screen.

A  B  C  D  E

Create File Using File.createNewFile() Method

File.createNewFile() method允许在给定位置或当前目录中创建文件，如下所示 −

File.createNewFile() method allows to create a file in given location or in current directory as follows −

Syntax

File file = new File("d://test//testFile1.txt");

//Create the file
if (file.createNewFile()) {
   System.out.println("File is created!");
} else {
   System.out.println("File already exists.");
}

Example: Create File Using File.createNewFile() Method

以下是使用 createNewFile() 方法在指定目录中创建文件的 File 示例代码：

Following is the example to demonstrate File to create a file in given directory using createNewFile() method −

package com.tutorialspoint;

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

public class FileTest {

   public static void main(String args[]) {

      try {
          File file = new File("d://test//testFile1.txt");

          //Create the file
          if (file.createNewFile()) {
             System.out.println("File is created!");
          } else {
             System.out.println("File already exists.");
          }

          // Write Content
          FileWriter writer = new FileWriter(file);
          writer.write("Test data");
          writer.close();


          // read content
          FileReader reader = new FileReader(file);

          int c;
          while ((c = reader.read()) != -1) {
        	  char ch = (char) c;
              System.out.print(ch);
          }
      } catch (IOException e) {
         System.out.print("Exception");
      }
   }
}

上面的代码将创建文件 test.txt，并将指定的字符串写入文本格式。stdout 屏幕上将有相同输出。

The above code would create file test.txt and would write given string in text format. Same would be the output on the stdout screen.

File is created!
Test data

Create File Using Files.write() Method

Files.write() 是一个较新型、更灵活的方法，可以在同一命令中创建文件并将内容写入文件，如下所示：

Files.write() is a newer and more flexible method create a file and write content to a file in same command as shown below −

Syntax

String data = "Test data";
Files.write(Paths.get("d://test/testFile3.txt"), data.getBytes());

List<String> lines = Arrays.asList("1st line", "2nd line");
Files.write(Paths.get("file6.txt"), lines, StandardCharsets.UTF_8,
   StandardOpenOption.CREATE, StandardOpenOption.APPEND);

Example: Create File Using Files.write() Method

以下是使用 Files.write() 方法在指定目录中创建文件的 File 示例代码：

Following is the example to demonstrate File to create a file in given directory using Files.write() method −

package com.tutorialspoint;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.Arrays;
import java.util.List;

public class FileTest {

   public static void main(String args[]) {

      try {
    	  String data = "Test data";
          Files.write(Paths.get("d://test/testFile3.txt"), data.getBytes());
          List<String> lines = Arrays.asList("1st line", "2nd line");
          Files.write(Paths.get(
             "file6.txt"), lines, StandardCharsets.UTF_8,
             StandardOpenOption.CREATE, StandardOpenOption.APPEND);

          List<String> content = Files.readAllLines(Paths.get("d://test/testFile3.txt"));

          System.out.println(content);

          content = Files.readAllLines(Paths.get("file6.txt"));

          System.out.println(content);
      } catch (IOException e) {
         System.out.print("Exception");
      }
   }
}

上面的代码将创建文件 test.txt，并将指定的字符串写入文本格式。stdout 屏幕上将有相同输出。

The above code would create file test.txt and would write given strings in text format. Same would be the output on the stdout screen.

[Test data]
[1st line, 2nd line]