reading a file through input streams in java

Question

how is the flow of execution directed in the code below.(how does 'i' get updated(or incremented)?

while((i=fr.read())!=-1)
{ System.out.print((char)i);
}

- See more at: http://tutorialspointexamples.com/filereader-and-filewriter-in-java/#sthash.QxSyiKRe.dpuf

amadan · Accepted Answer · 2017-01-16 12:14:43Z

1

Filereader.read reads a single character. It returns an int, which represents the character read.

in your code

while((i=fr.read())!=-1)
{ 
   System.out.print((char)i);
}

(i=fr.read()) resolves first, giving you the character read. The while loop will resolve this each time it loops, moving through the file.

The outer while then compares this value against -1.

If it does, the while loop ends.
If it doesn't match it outputs the character.

answered Jan 16, 2017 at 12:14

amadan

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3 Comments

pradeep Over a year ago

but how does the loop proceed since there is no updation for the counter variable( in this case i) in the loop.

amadan Over a year ago

i isn't a counter variable. i is the value that is returned by the read call. fr has an internal file pointer - read just tells it to read the next character. see tutorialspoint.com/java/java_filereader_class.htm

dumbPotato21 Over a year ago

@pradeep in other words, when there are no more characters to read, i would be set to -1, and the loop would terminate

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