[英]IntelliJ “result of inputstream.read is ignored” - how to fix?
我正在修復應用程序中的一些潛在錯誤。 我正在使用Sonar評估我的代碼。 我的問題是這樣的:
private Cipher readKey(InputStream re) throws Exception {
byte[] encodedKey = new byte[decryptBuferSize];
re.read(encodedKey); //Check the return value of the "read" call to see how many bytes were read. (the issue I get from Sonar)
byte[] key = keyDcipher.doFinal(encodedKey);
Cipher dcipher = ConverterUtils.getAesCipher();
dcipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(key, "AES"));
return dcipher;
}
這是否意味着字節數組為空? 為什么它被忽略? 我從未使用過字節,因此我想知道這個問題的確切含義以及如何解決。 感謝您的協助!
這是否意味着字節數組為空?
否-這不是錯誤
從以下定義看read(byte [])方法:
public abstract class InputStream extends Object implements Closeable {
/**
* Reads up to {@code byteCount} bytes from this stream and stores them in
* the byte array {@code buffer} starting at {@code byteOffset}.
* Returns the number of bytes actually read or -1 if the end of the stream
* has been reached.
*
* @throws IndexOutOfBoundsException
* if {@code byteOffset < 0 || byteCount < 0 || byteOffset + byteCount > buffer.length}.
* @throws IOException
* if the stream is closed or another IOException occurs.
*/
public int read(byte[] buffer, int byteOffset, int byteCount) throws IOException {
....
}
}
那么IDE指示什么呢? 是您省略了read方法的結果 -這是實際讀取的字節數,如果已到達流的末尾,則為-1。
怎么修?
如果您關心將多少字節讀取到字節緩沖區:
// define variable to hold count of read bytes returned by method
int no_bytes_read = re.read(encodedKey);
為什么你應該關心???
例如:
// on left define byte array = // on right reserve new byte array of size 10 bytes
byte[] buffer = new byte[10];
// [00 00 00 00 00 00 00 00 00 00] <- array in memory
int we_have_read = read(buffer); // assume we have read 3 bytes
// [22 ff a2 00 00 00 00 00 00 00] <- array after read
have we reached the end of steram or not ? do we need still to read ?
we_have_read ? what is the value of this variable ? 3 or -1 ?
if 3 ? do we need still read ?
or -1 ? what to do ?
我鼓勵您閱讀有關io和nio api的更多信息
http://tutorials.jenkov.com/java-nio/nio-vs-io.html
https://blogs.oracle.com/slc/entry/javanio_vs_javaio
http://www.skill-guru.com/blog/2010/11/14/java-nio-vs-java-io-which-one-to-use/
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