I have an InputStreamReader object. I want to read multiple lines into a buffer/array using one function call (without crating a mass of string objects). Is there a simple way to do so?
A:
First of all mind that InputStreamReader is not so efficient, you should wrap it around a BufferedReader object for maximum performance.
Taken into account this you can do something like this:
public String readLines(InputStreamReader in)
{
BufferedReader br = new BufferedReader(in);
// you should estimate buffer size
StringBuffer sb = new StringBuffer(5000);
try
{
int linesPerRead = 100;
for (int i = 0; i < linesPerRead; ++i)
{
sb.append(br.readLine());
// placing newlines back because readLine() removes them
sb.append('\n');
}
}
catch (Exception e)
{
e.printStackTrace();
}
return sb.toString();
}
Mind that readLine() returns null is EOF is reached, so you should check and take care of it.
Jack
2010-03-12 17:49:18
The objective in NOT to read line by lines, since it fills my heap with redundant string objects and makes the GC go wild. I wanted to read from an inputstreamreader (using a bufferedReader /whatever), without creating many String objects. Perhaps read directly into a buffer (without creating a string in the middle), or otherwise read multiple lines to avoid the string garbage...
amitlicht
2010-03-12 18:03:21
what about using a __RandomAccessFile__ to read directly a buffer of bytes? Also the whole file (__readFull(byte[] b)__)
Jack
2010-03-12 18:42:23
Strings are *very* optimized in JVM v. 1.6. Have you been using a profiler and really spotted an issue? Or are you just guessing?
incarnate
2010-03-12 21:29:52
A:
If you have some delimiter for multiple lines you can read that many characters using read method with length and offset. Otherwise using a StringBuilder for appending each line read by BufferedReader should work well for you without eating up too much temp memory
Fazal
2010-03-12 21:25:46