Java通过InputStream读取和写入文件操作

DataOutputStream outputStream  = null;
	InputStream inputStream = null;
	
	try {
		inputStream = new FileInputStream(sourcefile);
		outputStream = new DataOutputStream(new FileOutputStream(targetfile));
		int len = input.available();
		//判断长度是否大于1M
		if (len <= 1024 * 1024) {
			byte[] bytes = new byte[len];
			inputStream.read(bytes);
			outputStream.write(bytes);
		} else {
			int byteCount = 0;
			//1M逐个读取
			byte[] bytes = new byte[1024*1024];
			while ((byteCount = inputStream.read(bytes)) != -1){
				outputStream.write(bytes, 0, byteCount);
			}
		}
	} catch (Exception e) {
		e.printStackTrace();
	} finally {
		outputStream.flush();
		inputStream.close();
		outputStream.close();
	}