Logic is correct or not?

Question about the task

Tracking changes

Java Core, Level 9, Lesson 11

Under discussion

what i did wrong? or i didnt understand what the program neeeds.

Read 2 file names from the console: file1 and file2.
Both files contain text, but file2 is an updated version of file1. Some of the lines are still the same.
You need to create a merged version of the lines by writing them to the lines list.
The ADDED and REMOVED labels can't be used consecutively—they must always separated by the SAME label.
The example includes empty lines for clarity.
Neither the original file nor the updated file have empty lines!

Example 1:
original updated merged file1: file2: Result: (lines) line1 line1 SAME line1 line2 REMOVED line2 line3 line3 SAME line3 line4 REMOVED line4 line5 line5 SAME line5 line0 ADDED line0 line1 line1 SAME line1 line2 REMOVED line2 line3 line3 SAME line3 line4 ADDED line4 line5 line5 SAME line5 line0 REMOVED line0

Example 2:
original updated merged file1: file2: Result: (lines) line1 line1 SAME line1 line0 ADDED line0

In the example, empty lines mean that the line is not in the specified file.

Requirements:

The Solution class must contain a LineItem class.
The Solution class must have an enum called Type.
The Solution class must have a public static List<LineItem> field called lines that is initialized immediately.
In the main(String[] args) method, the program must read file names from the console (use BufferedReader).
In the main(String[] args) method, the BufferedReader used for reading input from the console must be closed after use.
The program must read the contents of the first and second file (use FileReader).
The file input streams (FileReader) must be closed.
The lines list should contain the merged version of the lines from the files. Each line should start with the label ADDED, REMOVED, or SAME, depending on the action taken.

package com.codegym.task.task19.task1916; import java.util.ArrayList; import java.util.List; import java.io.FileReader; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; /* Tracking changes */ public class Solution { public static List<LineItem> lines = new ArrayList<>(); public static void main(String[] args)throws IOException { BufferedReader b = new BufferedReader(new InputStreamReader(System.in)); String f1 = b.readLine(); String f2= b.readLine(); b.close(); BufferedReader f = new BufferedReader(new FileReader(f1)); BufferedReader ff = new BufferedReader(new FileReader(f2)); ArrayList<String> o = new ArrayList<>(); ArrayList<String> u = new ArrayList<>(); while(f.ready()){ o.add(f.readLine()); } f.close(); while(ff.ready()){ u.add(ff.readLine()); } ff.close(); for(int i=0,j=0;i<o.size()&&j<u.size();i++,j++){ if(o.get(i).equals(u.get(j))){ lines.add(new LineItem(Type.SAME,u.get(j))); } else if(o.get(i).equals(u.get(j+1))) { lines.add(new LineItem(Type.ADDED,u.get(j))); lines.add(new LineItem(Type.SAME,u.get(j+1))); } else if(u.get(j).equals(o.get(i+1))){ lines.add(new LineItem(Type.REMOVED,o.get(i))); lines.add(new LineItem(Type.SAME,o.get(i+1))); } } } public static enum Type { ADDED, // New line added REMOVED, // Line deleted SAME // No change } public static class LineItem { public Type type; public String line; public LineItem(Type type, String line) { this.type = type; this.line = line; } } }

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Sanjeevkumar

Level 22 , Mumbai, India

17 August 2020, 13:42

i changed it but it doesnt work. will you send your code?

Daniel Walbolt

Level 22 , Waterville, United States

16 August 2020, 18:14

The problem here is that when the code is iterating the last lines, "(j+1)" and "(i + 1)" are going to equal null, and throw an error (ArrayIndexOutOfBounds). I haven't tested your code, for any other problems but you need to make sure you increment j and i when you set the next 'set' as SAME. You put in Type.SAME, and u.get(j+1)/(i+1) but I think it should be (++j) and (++i).