Java中InputStream转File

一、文件流

方法一：

InputStream initialStream = new FileInputStream(new File("src/main/resources/sample.txt"));
byte[] buffer = new byte[initialStream.available()];
initialStream.read(buffer);
 
File targetFile = new File("src/main/resources/targetFile.tmp");
OutputStream outStream = new FileOutputStream(targetFile);
outStream.write(buffer);

方法二：

InputStream initialStream = new FileInputStream(new File("src/main/resources/sample.txt"));
byte[] buffer = new byte[initialStream.available()];
initialStream.read(buffer);
File targetFile = new File("src/main/resources/targetFile.tmp");
Files.write(buffer, targetFile);

方法三：

InputStream initialStream = FileUtils.openInputStream(new File("src/main/resources/sample.txt"));
File targetFile = new File("src/main/resources/targetFile.tmp");
FileUtils.copyInputStreamToFile(initialStream, targetFile);

二、File -> Stream -> File

输入流映射正在进行的数据流
如果输入流链接到正在进行的数据流上，如来自正在进行的链接的HTTP响应，此时可能无法一次读取整个流。这种情况下，我们需要确保一直读取到流的尽头。

File targetFile = new File("src/main/resources/targetFile.tmp");
try(InputStream initialStream = new FileInputStream(new File("src/main/resources/sample.txt"));
    OutputStream outStream = new FileOutputStream(targetFile)) {
    byte[] buffer = new byte[8 * 1024];
    int bytesRead;
    while ((bytesRead = initialStream.read(buffer)) != -1) {
        outStream.write(buffer, 0, bytesRead);
    }
} catch (Exception e) {
    e.printStackTrace();
}

另一种实现方式：

try (InputStream initialStream = new FileInputStream(new File("src/main/resources/sample.txt"))) {
    File targetFile = new File("src/main/resources/targetFile.tmp");
 
    java.nio.file.Files.copy(
            initialStream,
            targetFile.toPath(),
            StandardCopyOption.REPLACE_EXISTING);
} catch (Exception e) {
    e.printStackTrace();
}