CODEWITHSUNDEEP
javaarraysfile
user4132350
user4132350

Reputation:

Reading from file into Array

I have a file with numbers. It looks as follows:

1 2
3 4
5 6
7 8
9 10

The problem occurs while reading the numbers into Array.

Here is a piece of code:

Scanner file1 = new Scanner( new File("file1.txt") );

int lengt_h = 0;

// Here Eclipse crashes...
while( file1.hasNext() ) lengt_h++;

int[] numberArray = new int[lengt_h];

for(int i=0; i<numberArray.length; i++) {
        numberArray[i] = file1.nextInt();
}

for(int n: numberArray) System.out.print(numberArray[n] + " ");

Even if I change a hasNext() function into constant length (e.g 10), then numbers in numberArray Array looks as follows:

1 1 1 2 1 1 5 5 1 3

Why the code does not work properly?

Upvotes: 1

Views: 164

Answers (4)

Rustam
Rustam

Reputation: 6515

  1. problem with you code is you are not moving the Sacanner pointer in while loop so it were infinite loop.
  2. In your last for loop you are trying to access element from numberArray[n] which is wrong because n itself is a number from your array numberArray.

you can try this : 

 public static void main(String args[]) throws FileNotFoundException {
        Scanner file1 = new Scanner(new File("d:\\data.txt"));
        int lengt_h = 0;
        while (file1.hasNext()) {
            lengt_h++;
            file1.next();
        }
        file1 = new Scanner(new File("d:\\data.txt")); // again put file pointer at beginning
        int[] numberArray = new int[lengt_h];
        for (int i = 0; i < numberArray.length; i++) {
            numberArray[i] = file1.nextInt();       // read integer from file
        }
        for (int n : numberArray)
            System.out.print(n + " ");
    }

Upvotes: 2

barak manos
barak manos

Reputation: 30146

Try this:

List<Integer> numberArray = new ArrayList<Integer>();
while (file1.hasNext())
    numberArray.add(file1.nextInt());
for (Integer n : numberArray)
    System.out.print(n + " ");

Upvotes: 0

SMA
SMA

Reputation: 37083

Check the hasNext method here http://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#hasNext%28%29

it says "The scanner does not advance past any input."

So to move it further you should move to next token.

Upvotes: 0

Mitesh Pathak
Mitesh Pathak

Reputation: 1211

while( file1.hasNext() ) lengt_h++; // infi loop

hasNext method returns true if and only if this scanner has another token

public boolean hasNext()

You are not reading next token and hence hasNext() will always return true

[EDIT]

If you don't know the size of array in advance, its better to use ArrayList

[1] http://www.tutorialspoint.com/java/util/java_util_arraylist.htm

Upvotes: 1

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