在java中，如何从输入流中读取固定长度并保存为文件？

发布于 2024-12-13 00:19:25 字数 327 浏览 1 评论 0原文

在java中，如何从输入流中读取固定长度并保存为文件？例如。我想从 inputStream 读取 5M，并保存为 downloadFile.txt 或其他内容。(BUFFERSIZE=1024)

FileOutputStream fos = new FileOutputStream(downloadFile);
byte buffer [] = new byte[BUFFERSIZE];
int temp = 0;
while ((temp = inputStream.read(buffer)) != -1)
{
    fos.write(buffer, 0, temp);
}

原文

In java, how to read a fixed length from the inputstream and save as a file?
eg. I want to read 5M from inputStream, and save as downloadFile.txt or whatever.(BUFFERSIZE=1024)

FileOutputStream fos = new FileOutputStream(downloadFile);
byte buffer [] = new byte[BUFFERSIZE];
int temp = 0;
while ((temp = inputStream.read(buffer)) != -1)
{
    fos.write(buffer, 0, temp);
}

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智商已欠费 2024-12-20 00:19:25

两个选项：

继续阅读和写作，直到到达输入的末尾或复制了足够的内容：

byte[]缓冲区=新字节[1024];
int 左字节数 = 5 * 1024 * 1024； // 或者其他什么
FileInputStream fis = new FileInputStream(输入);
尝试 {
  FileOutputStream fos = new FileOutputStream(输出);
  尝试 {
    while (bytesLeft > 0) {
      int read = fis.read(buffer, 0, Math.min(bytesLeft, buffer.length);
      如果（读取==-1）{
        throw new EOFException(“数据意外结束”);
      }
      fos.write(缓冲区, 0, 读);
      bytesLeft -= 读取；
    }
  } 最后 {
    fos.close(); // 或者使用Guava的Closeables.closeQuietly,
                 // 或 Java 7 中的 try-with-resources
  }
} 最后 {
  fis.close(); 
}

一次调用将所有 5M 数据读入内存，例如使用 DataInputStream.readFully< /code>，然后一口气写出来。更简单，但明显占用更多内存。

Two options:

Just keep reading and writing until you either reach the end of the input or you've copied enough:

byte[] buffer = new byte[1024];
int bytesLeft = 5 * 1024 * 1024; // Or whatever
FileInputStream fis = new FileInputStream(input);
try {
  FileOutputStream fos = new FileOutputStream(output);
  try {
    while (bytesLeft > 0) {
      int read = fis.read(buffer, 0, Math.min(bytesLeft, buffer.length);
      if (read == -1) {
        throw new EOFException("Unexpected end of data");
      }
      fos.write(buffer, 0, read);
      bytesLeft -= read;
    }
  } finally {
    fos.close(); // Or use Guava's Closeables.closeQuietly,
                 // or try-with-resources in Java 7
  }
} finally {
  fis.close(); 
}

Read all 5M into memory in one call, e.g. using DataInputStream.readFully, and then write it out in one go. Simpler, but obviously uses more memory.

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