Some FileIO Practice

You will write three programs that will take files and display a portion of them to the screen. Feel free to frankencode from Grip.java as it has the basic template for reading a file line by line.

Here is a test file, test.dat you can run these on. Feel free to add lines.

533 221  443 221
444 321  425 222
889 cow  pig horse

Head.java this takes two command-line arguments and you run it like this.

unix> java Head 2 test.dat
533 221  443 221
444 321  425 222

This will print out the first (number) lines of file (filename).

Tail.java this takes two command-line arguments. You run it like this.

unix> java Tail 2 test.dat
444 321  425 222
889 cow  pig horse

This will print out the last (number) lines of code in the file.

Squawk.java This program extracts columns from a file with columnar data. Do not worry about checking on the numbrer of columns in the file.

java Squawk filename num1, num2, num3....

This takes as arguments a filename (filename) and a sequence of numerical arguments. The file is assumed to be a columnar file of date looking like this

unix> java test.dat 1 3  

533 433
444 425
889 pig

Here are some hints.

• read the file line by line
• For Tail.java, you might want to store the lines in an array list.
• For Squawk.java, split each line and use the indices in the resulting arrays to print out the entry for each column. To split a string use .split("\\s+). Make an integer array and use Integer.parseInt to convert the command-line arguments after ther file name into integers to populate the array. Then the printing of lines is easy.