- 文件处于磁盘上或者流处于内存中
在输入流有已知的和预处理的数据时,如在硬盘上的文件或者在流处于内存中。这种情况下,不需要做边界校验,并且内存容量条件允许的话,可以简单的读取并一次写入。
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);
基于Guava的实现
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);
基于Commons IO的实现
InputStream initialStream = FileUtils.openInputStream(new File("src/main/resources/sample.txt")); File targetFile = new File("src/main/resources/targetFile.tmp"); FileUtils.copyInputStreamToFile(initialStream, targetFile);
- 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(); }