I'm looking for the most time-efficient way to read STDIN line-by-line.
The first line is the number of conditions to test. All the following lines are conditions (strings) with a maximum of 100 000 characters.
I have already tried the following (plus result for 4 times 90 000 characters:
Scanner with a while-loop (7255 ms)
Scanner sc = new Scanner(System.in);
int numberOfLines = Integer.parseInt(sc.nextLine());
long start = 0;
int i = 1;
while (i<=numberOfLines){
start = System.currentTimeMillis();
sc.nextLine();
Debug.println((System.currentTimeMillis()-start) + "ms for scanner while");
i++;
}
Scanner with a for-loop (7078 ms)
Scanner sc = new Scanner(System.in);
int numberOfLines = Integer.parseInt(sc.nextLine());
long start = 0;
for (int i = 1; i<= numberOfLines;i++){
start = System.currentTimeMillis();
sc.nextLine();
Debug.println((System.currentTimeMillis()-start) + "ms for scanner for");
//i++;
}
BufferedReader with a for-loop (7403 ms)
try {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int numberOfLines = Integer.parseInt(br.readLine());
long start = 0;
for (int i = 0; i< numberOfLines;i++){
start = System.currentTimeMillis();
br.readLine();
Debug.println((System.currentTimeMillis()-start) + "ms for bufferreader for");
//i++;
}
} catch (Exception e) {
System.err.println("Error:" + e.getMessage());
}
BufferedReader with a while-loop (7461 ms)
try {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int numberOfLines = Integer.parseInt(br.readLine());
int i=0;
long start = 0;
while(i< numberOfLines){
start = System.currentTimeMillis();
br.readLine();
Debug.println((System.currentTimeMillis()-start) + "ms for bufferreader while");
i++;
}
} catch (Exception e) {
System.err.println("Error:" + e.getMessage());
}
While debugging the time taken, i noticed that the time-taken decreases after each read. Is it possible to restrict the bytes that are initialized (f.e. : If you have a maximum of 100.000 chars, limit the scanner/bufferedreader to only initialize 100 000 chars. After a read it will need to refill itself with the next 100 000 chars)
Any ideas on this matter are more than welcome.
EDIT : Added the code for each scenario along with the time-taken per line read. Also changed 100.000 to 100 000 to read more easily.
Looked inside BufferedReader#readLine
source. There're several problems I see:
You may take your chances with two things:
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