我惊奇地发现，今天我找不到任何简单的方法来用Java将InputStream的内容写入OutputStream。显然，编写字节缓冲区代码并不难，但我怀疑我只是缺少了一些可以使我的工作更简单(并且代码更清晰)的东西。
那么，给定一个InputStream in和一个OutputStream out，是否有一种更简单的方法来编写下面的代码?
byte[] buffer = new byte[1024];
int len = in.read(buffer);
while (len != -1) {
out.write(buffer, 0, len);
len = in.read(buffer);
}
当前回答
你可以使用这种方法
public static void copyStream(InputStream is, OutputStream os)
{
final int buffer_size=1024;
try
{
byte[] bytes=new byte[buffer_size];
for(;;)
{
int count=is.read(bytes, 0, buffer_size);
if(count==-1)
break;
os.write(bytes, 0, count);
}
}
catch(Exception ex){}
}
其他回答
使用Java7和try-with-resources，提供了一个简化且可读的版本。
try(InputStream inputStream = new FileInputStream("C:\\mov.mp4");
OutputStream outputStream = new FileOutputStream("D:\\mov.mp4")) {
byte[] buffer = new byte[10*1024];
for (int length; (length = inputStream.read(buffer)) != -1; ) {
outputStream.write(buffer, 0, length);
}
} catch (FileNotFoundException exception) {
exception.printStackTrace();
} catch (IOException ioException) {
ioException.printStackTrace();
}
我使用ByteStreamKt。copyTo(src, dst, buffer.length)方法
这是我的代码
public static void replaceCurrentDb(Context context, Uri newDbUri) {
try {
File currentDb = context.getDatabasePath(DATABASE_NAME);
if (currentDb.exists()) {
InputStream src = context.getContentResolver().openInputStream(newDbUri);
FileOutputStream dst = new FileOutputStream(currentDb);
final byte[] buffer = new byte[8 * 1024];
ByteStreamsKt.copyTo(src, dst, buffer.length);
src.close();
dst.close();
Toast.makeText(context, "SUCCESS! Your selected file is set as current menu.", Toast.LENGTH_LONG).show();
}
else
Log.e("DOWNLOAD:::: Database", " fail, database not found");
}
catch (IOException e) {
Toast.makeText(context, "Data Download FAIL.", Toast.LENGTH_LONG).show();
Log.e("DOWNLOAD FAIL!!!", "fail, reason:", e);
}
}
使用Commons Net的Util类:
import org.apache.commons.net.io.Util;
...
Util.copyStream(in, out);
可读性不是很好，但是很有效，没有依赖关系，可以在任何java版本上运行
byte[] buffer=new byte[1024];
for(int n; (n=inputStream.read(buffer))!=-1; outputStream.write(buffer,0,n));
JDK使用相同的代码，因此似乎没有“更简单”的方法，没有笨重的第三方库(可能不会做任何不同的事情)。下面是直接从java.nio.file.Files.java中复制的:
// buffer size used for reading and writing
private static final int BUFFER_SIZE = 8192;
/**
* Reads all bytes from an input stream and writes them to an output stream.
*/
private static long copy(InputStream source, OutputStream sink) throws IOException {
long nread = 0L;
byte[] buf = new byte[BUFFER_SIZE];
int n;
while ((n = source.read(buf)) > 0) {
sink.write(buf, 0, n);
nread += n;
}
return nread;
}
