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POjava: read from text file and make objects of it and add to collections and then sort
 

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  1. POjava: read from text file and make objects of it and add to collections and then sort
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    <p>What i want to do is:</p> <ol> <li>Create an Employee class having private fields as mentioned in any of the file.</li> <li>Read the content from the files(there are 150 files) in the folder and create employee object for each file.</li> <li>Store the Employee objects created in a Collection</li> <li>Create methods which would sort the employee collection according to the different fields in ascending and descending order.</li> </ol> <p>And my code for the 1st 3 lines is:</p> <pre><code>package com.fulcrum.emp; import java.io.File; import java.io.FileNotFoundException; import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; import java.util.List; import java.util.Scanner; public class TestingColections { public static void main(String[] args) { File folder = new File("D:\\employee files"); File[] listOfFiles = folder.listFiles(); ArrayList&lt;Employee&gt; emp = null; int id = 0; String name = null; int age = 0; for (File file : listOfFiles) { try { Scanner scanner = new Scanner(file); String tokens = ""; String[] newtokens = null; while (scanner.hasNext()) { tokens = tokens.concat(scanner.nextLine()).concat(" "); tokens = tokens.replace("=", "|"); newtokens = tokens.split("[|\\s]"); } id = Integer.parseInt(newtokens[1]); name = (newtokens[3] + " " + newtokens[4]); age = Integer.parseInt(newtokens[6]); emp = new ArrayList&lt;Employee&gt;(); emp.add(new Employee(id, name, age)); } catch (FileNotFoundException e) { e.printStackTrace(); } } } } </code></pre> <p>My problem is instead of just <code>add(</code>) I tried to add object in a specified index using for loop but it gave <code>IndexOutOfBoundException</code>.<br>How can i do that?can anyone please help?<br> And also I want to sort those abjects according to different field.<br>Please guide me on that too.</p>
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    1. USShreyos Adikari
    1. USuser2412380
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    1. COYou initialize `emp` in the middle of your loop, so each time you read a file, you destroy your work with the previous one. Simply write `List<Employee> emp = new ArrayList<>();` near the top of `main`. Better yet, don't do everything in `main`. Flesh out your class with instance variables and methods, create one with `TestingCollections tc = new TestingCollections()`, and have `tc` do something. Then, you can break up your work into smaller methods, and *test them*. `TestingCollections` is a bad name too.
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      1. USEric Jablow
    2. COyeahh u r rite..its working now... :) its print all 150 employeess objects..but how do i sort according to different fields..please help me to solve that
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    3. CODoes `Employee` implement `Comparable`? If so, you can call `Collections.sort(emp)`. If not, or if you need to sort different ways at different times, create implementations of `Comparator<Employee>` and call `Collections.sort(emp, theComparator)`. Look up those interfaces; you might need a comparator for `id`s and another for `name`s. Try going through the Java Tutorial for practice.
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      1. USEric Jablow
 

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