Reading a (text) data file to read and parse a text file (as in the wireframe data files), the JDK supplied Scanner class is a useful utility

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159.235 Assignment 2 Notes

Reading a (text) data file

To read and parse a text file (as in the wireframe data files), the JDK supplied Scanner class is a useful utility:

// Need these imports

import java.io.File;

import java.io.FileNotFoundException; import java.util.Scanner;

 

try {

 

// Instantiate a Scanner for the given File object

Scanner scanner = new Scanner(myFile);

 

/// code here . . .

}

 

// I f you create a Scanner instance , you must handle this exception

catch (FileNotFoundException e) { e.printStackTrace();

}

To access the next line in the file, simply do:

line = scanner.nextLine();

where line has previously been declared as String.

Given that line is a String, you need to do an appropriate conversion to integer or float- ing point if that’s what you want. You can do this with either Integer.parseInt() or Double.parseDouble(). For example, to read the first line of the wireframe data files:

line = scanner.nextLine();

int numVertices = Integer.parseInt(line);

If a line has multiple data items, you can split the line using a StringTokenizer, which you can access by first importing:

import java.util.StringTokenizer;

So, for example, if the line looked like:

2.31879 -1.29409 -0.673863

Then you can split this line into doubles as follows:

line = scanner.nextLine();

StringTokenizer strtok = new StringTokenizer(line, " \t"); x = Double.parseDouble(strtok.nextToken());

y = Double.parseDouble(strtok.nextToken()); z = Double.parseDouble(strtok.nextToken());

A similar procedure would be used if dealing with a line of ints

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