Question

Write a Java class called CityDistances in a class file called CityDistances.java.   

2. Your methods will make use of two text files. a. The first text file contains the names of cities. However, the first line of the file is a number specifying how many city names are contained within the file. For example,

5

Dallas

Houston

Austin

Nacogdoches

El Paso

b. The second text file contains the distances between the cities in the file described above. This file does not contain an entry for how many distances are within the file. If, as in the example above, there are five (5) city names in the first text file, then this text file should contain 52 = 25 distance entries. The first entry should always be zero (since Dallas is a distance of zero miles from itself). The second entry is the distance from Dallas to Houston, and the third entry is the distance from Dallas to Austin, etc.

3. The CityDistances class contains four static methods: a. A public method called loadCities() that opens the file, reads in the data and returns a one-dimensional array of String containing the city names stored in the file. The method takes a single argument called filename of type String that is the name of the file to be opened. The first item read from the text file should be the number of city names within the file (read as an integer). If done correctly, the returned array should be the correct size to store all city names without any “extra” space within the array. If the file does not exist or a problem reading the file is encountered, then an IOException is thrown. Hint: Be aware that using the nextInt() method from the Scanner class will read the number but not the newline character found after the number. Your method should correctly handle the newline character.

b. A public method called loadDistances() that opens the file, reads in the data and returns a two-dimensional array of double containing the city distances stored in the file. The method takes an argument called filename of type String that is the name of the file to be opened and an argument called numCities of type int corresponding to the number of cities that were listed in the text file read by loadCities(). If done correctly, the returned two-dimensional array should be an n x n array where n is the number of cities represented and organized such that each row corresponds to the distances from a particular city. If the file does not exist or a problem reading the file is encountered, then an IOException is thrown.

Answer 1

If you have any doubts, please give me comment....

import java.io.*;

import java.util.Scanner;

public class CityDistances {

public static String[] loadCities(String fname) throws IOException {

Scanner fileIn = new Scanner(new File(fname));

int n = fileIn.nextInt();

String[] cities = new String[n];

fileIn.nextLine();

int i = 0;

while (fileIn.hasNextLine()) {

cities[i] = fileIn.nextLine();

i++;

}

fileIn.close();

return cities;

}

public static double[][] loadDistances(String fname, int numCities) throws IOException {

double distances[][] = new double[numCities][numCities];

Scanner fileIn = new Scanner(new File(fname));

for (int i = 0; i < numCities; i++) {

for (int j = 0; j < numCities; j++) {

distances[i][j] = fileIn.nextInt();

}

}

fileIn.close();

return distances;

}

}