从inputStream中读取指定长度的字节

java 中如何从InputStream中读取指定长度的字节呢？

代码如下：

/***
	 * 从输入流获取字节数组,当文件很大时，报java.lang.OutOfMemoryError: Java heap space
	 * 
	 * @since 2014-02-19
	 * @param br_right
	 * @param length2
	 * @return
	 * @throws IOException
	 */
	public static byte[] readBytesFromInputStream(InputStream br_right,
			int length2) throws IOException {
		int readSize;
		byte[] bytes = null;
		bytes = new byte[length2];

		long length_tmp = length2;
		long index = 0;// start from zero
		while ((readSize = br_right.read(bytes, (int) index, (int) length_tmp)) != -1) {
			length_tmp -= readSize;
			if (length_tmp == 0) {
				break;
			}
			index = index + readSize;
		}
		return bytes;
	}
/***
	 * 读取指定长度的字节
	 * @since 2014-02-27
	 * @param ins
	 * @param sumLeng : 要读取的字节数
	 * @return
	 * @throws IOException
	 */
	public static byte[]readBytesFromGzipInputStream(GZIPInputStream ins,long sumLeng) throws IOException{
		byte[] fileNameBytes = new byte[(int) sumLeng];
		int fileNameReadLength=0;
		int hasReadLength=0;//已经读取的字节数
		while((fileNameReadLength=ins.read(fileNameBytes,hasReadLength,(int)sumLeng-hasReadLength))>0){
			hasReadLength=hasReadLength+fileNameReadLength;
		}
		return fileNameBytes;
	}
/***
	 * read char array from inputstream according to specified length.
	 * 
	 * @param file
	 * @param ins
	 * @param length2
	 *            :要读取的字符总数
	 * @throws IOException
	 */
	public static char[] getCharsFromInputStream(BufferedReader br_right,
			int length2) throws IOException {
		int readSize;
		char[] chars = null;
		chars = new char[length2];

		long length_tmp = length2;
		long index = 0;// start from zero
		while ((readSize = br_right.read(chars, (int) index, (int) length_tmp)) != -1) {
			length_tmp -= readSize;
			if (length_tmp == 0) {
				break;
			}
			index = index + readSize;// 写入字符数组的offset（偏移量）
		}
		return chars;
	}

/***
	 * 从文件中读取指定长度的字符（注意：不是字节）
	 * 
	 * @param file
	 * @param length2
	 * @return
	 * @throws IOException
	 */
	public static char[] getCharsFromFile(File file, int length2)
			throws IOException {
		FileInputStream fin = new FileInputStream(file);
		InputStreamReader inr = new InputStreamReader(fin);
		BufferedReader br = new BufferedReader(inr);
		return getCharsFromInputStream(br, length2);
	}
private static byte[] readDataFromLength(HttpURLConnection huc,
			int contentLength) throws Exception {

		InputStream in = huc.getInputStream();
		BufferedInputStream bis = new BufferedInputStream(in);

		// 数据字节数组
		byte[] receData = new byte[contentLength];

		// 已读取的长度
		int readAlreadyLength = 0;

		// while ((readAlreadyLength+= bis.read(receData, readAlreadyLength,
		// contentLength-readAlreadyLength))< contentLength) {
		// System.out.println("right");
		// }
		while ((readAlreadyLength = readAlreadyLength
				+ bis.read(receData, readAlreadyLength, contentLength
						- readAlreadyLength)) < contentLength) {
		}
		// System.out.println("readLength=" + readLength);
		return receData;
	}

 

 

参考我的另外一篇博客：http://hw1287789687.iteye.com/blog/2019425