Two java homework

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.StringTokenizer;

/**

* Read a .dat file and reverse it.

*/

public class Reverse {

public static void main(String[]args) {

if (args.length != 3) {

System.err.println(" Incorrect number of arguments");

System.err.println(" Usage: ");

System.err.

println("\tjava Reverse <stack type> <input file> <output file>");

System.exit(1);

}

boolean useList = true;

if (args[0].compareTo("list")==0)

useList = true;

else if (args[0].compareTo("array")==0)

useList = false;

else {

System.err.println("\tSaw "+args[0]+" instead of list or array as first argument");

System.exit(1);

}

try {

//

// Set up the input file to read, and the output file to write to

//

BufferedReader fileIn =

new BufferedReader(new FileReader(args[1]));

PrintWriter fileOut =

new PrintWriter(new

BufferedWriter(new FileWriter(args[2])));

//

// Read the first line of the .dat file to get sample rate.

// We want to store the sample rate value in a variable,

// but we can ignore the "; Sample Rate" part of the line.

// Step through the first line one token (word) at a time

// using the StringTokenizer. The fourth token is the one

// we want (the sample rate).

//

StringTokenizer str;

String oneLine;

int sampleRate;

String strJunk;

oneLine = fileIn.readLine();

str = new StringTokenizer(oneLine);

strJunk = str.nextToken(); // Read in semicolon

strJunk = str.nextToken(); // Read in "Sample"

strJunk = str.nextToken(); // Read in "Rate"

// Read in sample rate

sampleRate = Integer.parseInt(str.nextToken());

//

// Read in the remainder of the file on line at a time.

// The values in the first column are thrown away.

// Place values from the second column on the stack.

// Stop reading if we reach the end of the file.

//

DStack s;

if (useList)

s = new ListStack();

else

s = new ArrayStack();

String timestep;

double data;

int count = 0;

while ((oneLine = fileIn.readLine()) != null) {

if (oneLine.charAt(0) == ';') {

continue;

}

str = new StringTokenizer(oneLine);

// Read in time step value from first column

timestep = str.nextToken();

// Read in data value from second column

data = Double.parseDouble(str.nextToken());

s.push(data);

count++;

}

System.out.println(count+" samples in file");

//

// Print the data values to output .dat file.

// First, output the header line:

// "; Sample Rate <sample rate>"

//

fileOut.println("; Sample Rate " + sampleRate);

// Since the first column consists of numbers which start

// at 0 and increase by 1/sampleRate every time slice, we'll

// just use numSteps to recalculate these numbers.

int numSteps = 0;

// Finally, we print the values in reverse order (by popping

// them off the stack). The first column consists of numbers

// which start at 0 and increase by 1/sampleRate per row, so

// we'll use numSteps/sampleRate to recalculate the appropriate

// values. Print a tab for uniform spacing.

while (!s.isEmpty()) {

fileOut.println((double) numSteps / sampleRate + "\t" +

s.pop());

numSteps++;

}

//

// Close the files

//

fileIn.close();

fileOut.close();

} catch(IOException ioe) {

System.err.

println

("Error opening/reading/writing input or output file.");

System.exit(1);

} catch(NumberFormatException nfe) {

System.err.println(nfe.toString());

System.err.println("Error in file format");

System.exit(1);

}

}

}