Write a Java program that reads a large file of strings and determines whether a

Question

Write a Java program that reads a large file of strings and determines whether all the strings are unique. As you read the file, generate a frequency histogram of the lengths of all the strings you read in. The filenames will start with either "3x3" or "4x4". Using this fact you can deduce that a filename starting with '3' will not have any string in that file greater than 3x3=9 chars long. A filename starting with '4' will be guaranteed to have no more than a string of length 4x4=16 chars. Use this fact to know how big of an array to declare for your histogram without having to read the strings from the file. My code: import java.util.*; import java.io.*; public class Program7 { public static void main( String args[] ) throws Exception { ArrayList list = new ArrayList(); BufferedReader infile = new BufferedReader( new FileReader( args[0] ) ); int maxLen= 16; // CHANGE THIS: a 3x3 grid has a max string length of 9, 4x4 grid has a max string length of 16 int[] histogram = new int[maxLen]; // because out inputfile is a 4 by 4 longest string can only be 16 long startTime = System.currentTimeMillis(); while (infile.ready()) { // right now this is an infinite loop // read in the strings and generate the freq histogram list.add( infile.readLine() ); } infile.close(); System.out.printf( "List contains %d Strings. ",list.size()); System.out.println("LEN FREQ"); for ( int i = 0; i < histogram.length ; ++i) // System.out.printf( "- %d ",i,histogram[i] ); boolean unique = true; int indexOfDupe = 0; // Look at the Strings in the list and set unique to fasle if you find any dupes if (unique) System.out.println("List has NO dupes."); else System.out.println("List has dupes at index position: " + indexOfDupe ); long endTime = System.currentTimeMillis(); long ms = endTime-startTime; System.out.printf("Elapsed time: %f seconds ", ms/1000.0); } }

Explanation / Answer

i have written this program which works and uses brute force .there is some changes i have made in the code.

import java.util.*;
import java.io.*;

public class Program7 {
        public static void main( String args[] ) throws Exception {
                ArrayList<String> list = new ArrayList<String>(); // create a new arraylist
                try {
                        File file = new File(args[0]);         // create a file object
                        System.out.println(args[0]);
                        FileReader fileReader = new FileReader(file);
                        BufferedReader bufferedReader = new BufferedReader(fileReader);
                        String line;
                        System.out.println(args[0].toString().substring(0,1)); // find the first character of filename
                        int length = Integer.parseInt(args[0].substring(0,1));
                        // add each line of file to list
                        while ((line = bufferedReader.readLine()) != null) {
                                list.add(line);
                        }
                        fileReader.close();
                        // find the size of list
                        if ( list != null ){
                                int len = list.size();
                        /* create a histogram array which stores the length of string . you created histogram array which was of wrong size you created array of size which is maximum length of string .we have to store the length of each string which is len not length. */
                        int[] histogram = new int[len];
                        long startTime = System.currentTimeMillis();
                        //brute forrce
                        for ( int i = 0;i < len ;i++){
                                for ( int j = i+1 ; j < len ;j++)
                                        if (list.get(i).equals(list.get(j)) )
                                                System.out.println( " string at index " + i + "matches string at index " + j);
                                histogram[i] = list.get(i).length(); // add length to histogram
                        }
                        // print histogram
                        for ( int i = 0 ; i < len ; i++ ){
                                System.out.printf("(%4d) | ",i);
                                for ( int j = 0 ; j < histogram[i] ; j ++ )
                                        System.out.print("*");
                                System.out.println("("+histogram[i]+")");
                        }
                        System.out.print("        ");
                        for ( int i = 0 ; i < length*length;i++)
                                System.out.print("_");
                        System.out.println();
                        long endTime = System.currentTimeMillis();
                        long ms = endTime-startTime;
                        System.out.printf("Elapsed time: %d seconds ", ms);

                        }
                } catch (Exception e) {
                        e.printStackTrace();
                }
        }
}

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