There's no first parameter... I get ArrayIndexOutOfBoundsException

Question about the task

Using TreeSet

Java Collections, Level 6, Lesson 8

Under discussion

Is there a bug in this task because it seems like there's no filename as the first parameter in the main method...

The first parameter is the file name: file1.
file1 only contains Latin letters, spaces, punctuation, dashes, and carriage returns.
Sort the letters alphabetically and display the first 5 unique letters on a single line without separators.
If there are less than 5 unique letters in file1, then display them all.
Uppercase and lowercase letters should be treated as the same letter.
The displayed result is not case sensitive.
Close the streams.

Example 1 - input file data:
zBk yaz b-kN

Example 1 - output:
abkny

Example 2 - input file data:
caAC A, aB? bB

Example 2 - output:
abc

Hint: use TreeSet

Requirements:

The program must use the TreeSet class.
Call the TreeSet object's add method to add elements.
The program must display the result on the screen.
The program's output must correspond to the task conditions.

package com.codegym.task.task36.task3605; import java.io.*; import java.util.NoSuchElementException; import java.util.TreeSet; /* Using TreeSet */ public class Solution { private static final String letters = "abcdefghijklmnopqrstuvwxyz"; public static void main(String[] args) throws IOException, ArrayIndexOutOfBoundsException { TreeSet<Character> treeSet = new TreeSet<>(); String file1 = args[0]; File file = new File(file1); BufferedReader in = new BufferedReader(new FileReader(file)); char[] buffer = new char[(int)file.length()]; in.read(buffer); in.close(); for (char c : buffer){ if (letters.indexOf(Character.toLowerCase(c)) >= 0); treeSet.add(Character.toLowerCase(c)); } for (int i=0;i<5;i++){ try { System.out.print(treeSet.first()); treeSet.remove(treeSet.first()); } catch (NoSuchElementException ignored){ break; } } } }

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Wei Cui

Level 39 , Newark, United States

21 April 2020, 19:43

public static void main(String[] args) throws IOException {
        TreeSet<Character> treeSet = new TreeSet<>();
        try {
            BufferedReader fileReader = new BufferedReader(new FileReader(args[0]));
            while (fileReader.ready()) {
                // An alphabetic character: = [\\p{Lower}\\p{Upper}]
                String line = fileReader.readLine().toLowerCase().replaceAll("[^\\p{Alpha}]","");
                for (char c : line.toCharArray())
                    treeSet.add(c);

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

        Iterator<Character> iterator = treeSet.iterator();
        int len = treeSet.size() < 5 ? treeSet.size() : 5;
        for (int i = 0; i < len; i++) {
            System.out.print((iterator.next()));
        }

    }

Seb

Level 41 , Crefeld, Germany

23 February 2020, 13:59

Your output is not quite right. You should only output letters from a-z. Correct line 24. I guess something like - if (letters.contains(String.valueOf(c).toLowerCase())) - should work.