Assignment #6: Sorting Program

[Modified Exercise 8.27]: Write a simple sorting utility, sort. The sort command takes a file name as a parameter. The file contains a sequence of lines; each line contains fields. By default, the fields are separated by white space (space or tab, in any amount), but the -t option allows you to use any one character as a field separator. By default fields are to be interpreted as strings, but the -n option allows you to interpret a field as a (double) number. The -r option reverses the order of the comparisons. Thus the sort proceeds from largest to smallest. The -f option makes the sort case-insensitive. Finally, by default lines are to be sorted as if the entire line was a single string (breaking ties arbitrarily). However, the -k option can be used to specify that the sort is performed using a specified field.

Options may appear in any order. The file name may appear anywhere; if it is not present, use System.in. You may not assume that there is a limiton the number of fields. The sorted output is written to System.out.

Examples

If the command is

java Sort -n -t: -k2 fileName

and the data file fileName is

10:20:30:40
20:100:40:30
30:40:10:20

Then the output is sorted on the basis of the second field, which is interpreted as a number, and is thus

10:20:30:40
30:40:10:20
20:100:40:30

Without the -n option, the output would be

20:100:40:30
10:20:30:40
30:40:10:20

Without any options, each line would be viewed as a giant string. The resulting output would be

10:20:30:40
20:100:40:30
30:40:10:20

Unusual Circumstances

If the file doesn't open, a line does not have enough fields, or a field that is to be a number can't be a number, then you have to do something reasonable. I will accept anything reasonable, but you have to document the behavior. You also must perform other checks, including verification that the command-line arguments make sense. For instance, a character must follow -t and -k.

Algorithms

You may use any of the sorting algorithms in java.util.Arrays; most likely you will want the version that takes an array and a comparator. Then, you can define a class that stores the complete line (as a String) and the key, on which the sort is based. Since the key could be either a double or a String, the logical declaration is:

class Line
{
  String theLine;
  Object theKey;
}

You would then define a Comparator that would compare any two Line objects, according to the options passed by the user. At this point, you need to hook everything together, and much of the work is parsing the command-line arguments and then the lines.

Java Notes

I suggest that some method accept an InputStream as a parameter; that InputStream will receive either the InputStream from a successfully opened file or System.in. Don't forget your buffering.
There are many ways to convert a String into a double. The easiest is probably Double.parseDouble.

Submission Details

I will provide several good test cases of various sizes, using various options, and two additional test cases that are degenerate. Look for them to eventually appear.

Submit all your source code, and the results of running the program on the test cases.
You must also provide a man page that explains what your program does. In particular, tell me how you handle degenerate cases. See javac docs for an example of reasonable documentation. I expect a professional job -- type it! The man page is important components of your grade.