How to read integer values ​​from a text file

Question

Possible duplicate:
Java: reading integers from file to array

I want to read integer values ​​from say contactids.txt text file. in the file i have values ​​like

12345 3456778 234234234 34234324234 

i Want to read them from a text file ... please help

Answer 1

You might want to do something like this (if you are using java 5 or more)

 Scanner scanner = new Scanner(new File("tall.txt")); int [] tall = new int [100]; int i = 0; while(scanner.hasNextInt()) { tall[i++] = scanner.nextInt(); } 

Via Julian Grenier of Reading Integers from a File in an Array

Answer 2

You can use Scanner and nextInt() . The scanner also has nextLong() for large integers.

Answer 3

Try the following: -

 File file = new File("contactids.txt"); Scanner scanner = new Scanner(file); while(scanner.hasNextLong()) { // Read values here like long input = scanner.nextLong(); } 

Answer 4

use the FileInputStream readLine () method to read and parse the returned String for int using the Integer.parseInt () method.

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Answer 5

How big are the values? Java 6 has a Scanner class that can read anything from int (32-bit), long (64-bit) to BigInteger (an arbitrary large integer).

There is a scanner for Java 5 or 4, but BigInteger support is not supported. You must read line by line (using the readLine of the Scanner class) and create a BigInteger object from line.

Answer 6

I would use almost the same, but with a list as a buffer for integers:

 static Object[] readFile(String fileName) { Scanner scanner = new Scanner(new File(fileName)); List<Integer> tall = new ArrayList<Integer>(); while (scanner.hasNextInt()) { tall.add(scanner.nextInt()); } return tall.toArray(); }