bufferedreader | 易学教程

How java.io.Buffer* stream differs from normal streams?

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问题 1) How does buffered streams work in background, how do they differ from normal streams and what are the advantage(s) of using them? 2) DataInputStream is also Byte based. But it is having methods to readLine() . What's the point in here? 回答1: From the BufferedInputStream javadoc: A BufferedInputStream adds functionality to another input stream-namely, the ability to buffer the input and to support the mark and reset methods. When the BufferedInputStream is created, an internal buffer array

CipherInputStream is Empty when trying to decrypt file

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问题 I'm trying to write a few helper methods to take care of reading and writing an encrypted file. I have two methods which successfully fulfill this and return an InputStream or an OutputStream (which are really the Cipher version) that I can use to read or write to the file. I have confirmed that these methods work peachy keen when wrapped with an Object stream and used to read and write an encrypted Object to file. However, the problem arises when I try to read from an encrypted text file. I

Can BufferedReader continue to read line in text file when pass to another function?

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I have this function to read text file with BufferedReader. I want to know if I can called another function and pass the readline/continue to read text file. If it can pass, can it loop the same function? A BufferedReader object is self-contained (thanks to Java's heavy emphasis on Object Orientation ), so you are free to pass it between functions and inside loops, and it will retain it's state - including the read line. However, if you are trying to call a method to process the line you have just read, then it would be much more efficient to pass the line itself to the method as a String ,

Reading text file and skipping blank lines until EOF is reached

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I am trying to read csv file full of text; however if there is a blank line in the middle somewhere, the whole thing breaks and I get a: java.lang.RuntimeException: java.lang.StringIndexOutOfBoundsException How would I go about removing/ignoring blank lines as long as it's not the end of the file? file = new FileReader(fileName); @SuppressWarnings("resource") BufferedReader reader = new BufferedReader(file); while ((line = reader.readLine()) != null) { //do lots of stuff to sort the data into lists etc } } catch (Exception e) { System.out.println("INPUT DATA WAS NOT FOUND, PLEASE PLACE FILE

Stop reading input in java without EOF

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In this question, how do i stop reading input? My program just keeps running, asking for more input. public static void main(String[] args) throws Exception { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String src; while ((src = br.readLine()) != null) { String trgt = br.readLine(); //do something } } Like this, public static void main(String[] args) throws Exception { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String src; while ((src = br.readLine()) != null) { StringTokenizer st=new StringTokenizer(src); if(!st.hasMoreTokens())

Use BufferedReader and InputStream together

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问题 I use a BufferedReader to read lines from an InputStream. When I read something directly from the InputStream, the BufferedReader ignores my read and continues reading at the same location. Is it possible to prevent this behavior? If not what is a good practice to do this? PS: Here's my code: byte[] ba = new byte[1024*1024]; int off = 0; int len = 0; do { len = Integer.parseInt(br.readLine()); in.read(ba, off, len); br.readLine(); off += len; } while(len > 0); in is my inputstream and br my

BufferedReader readLine used in while loop

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I have seen BufferedReader using while loops to iterate through the contents of a file, with code more or less like: try { FileReader fr = new FileReader(file); Buffered Reader br = new BufferedReader(fr); String line; while ( (line = br.readLine()) != null ) { // do something } } catch () {} what I don't understand is how the while loop is internally incrementing its counter until it has read all lines in the document. To me, the while loop above means "if the first line (line[0]) is not null, do something (presumably an infinite number of times)", and never advancing past the first line of

Java Process cannot get the InputStream through Runtime.getRunTime().exec()

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问题 try { String str; Process process = Runtime.getRuntime().exec("bash /home/abhishek/workspace/Pro/run"); InputStream isout = process.getInputStream(); InputStreamReader isoutr = new InputStreamReader(isout); BufferedReader brout = new BufferedReader(isoutr); while ((str = brout.readLine()) != null) { System.out.println(str); } } catch (IOException e) { e.printStackTrace(); } The Code has issues with getting the InputStream from the Process, because if I run the Shell script from my Terminal it

multiprocessing.pool.MaybeEncodingError: Error sending result: Reason: 'TypeError(“cannot serialize '_io.BufferedReader' object”,)'

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问题 I get the following error: multiprocessing.pool.MaybeEncodingError: Error sending result: '<multiprocessing.pool.ExceptionWithTraceback object at 0x7f758760d6a0>'. Reason: 'TypeError("cannot serialize '_io.BufferedReader' object",)' When running this code: from operator import itemgetter from multiprocessing import Pool import wget def f(args): print(args[1]) wget.download(args[1], "tests/" + target + '/' + str(args[0]), bar=None) if __name__ == "__main__": a = Pool(2) a.map(f, list(enumerate

Android app taking forever to download web content as string (WaitForGcToComplete blocked for xx.xxxms for cause HeapTrim?)

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问题 I'm new to Android development and am trying to make an app that simply downloads the source code of a given webpage as a string and displays it in the log. I have it working, and for google.com, it works fairly quickly. For my desired webpage, however, it takes EIGHT MINUTES, even though my computer's web browser can load it in only a few seconds. During these eight minutes, four messages are displayed over and over again in the log, with varying values. They are: W/art: Suspending all