Woah ok I'm lost.

Question about the task

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I'm trying to figure out a basic thing (I know, "haha") about putting this char Array in reverse order...probably forgetting something. Really confused! Any help would be awesome :'D

1. Read a file name from the console. Read the contents of the file.
2. For each line in the file:
2.1. reverse the order of all characters.
2.2. display the result.
3. Close the streams.

Example input file:
I'm a programmer. Amigo

Example result:
.remmargorp a m'I ogimA

Requirements:

The program must read the file name from the console (use BufferedReader).
The BufferedReader used for reading input from the console must be closed after use.
The program must read the file's contents (use FileReader).
The file input stream (FileReader) must be closed.
The program should display all of the characters from the file in reverse order.

package com.codegym.task.task19.task1926; /* Mirror image 1. Read a file name from the console. Read the contents of the file. 2. For each line in the file: 2.1. reverse the order of all characters. 2.2. display the result. 3. Close the streams. Example input file: I'm a programmer. Amigo Example result: .remmargorp a m'I ogimA Requirements: 1. The program must read the file name from the console (use BufferedReader). 2. The BufferedReader used for reading input from the console must be closed after use. 3. The program must read the file's contents (use FileReader). 4. The file input stream (FileReader) must be closed. 5. The program should display all of the characters from the file in reverse order. */ import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.io.InputStreamReader; public class Solution { public static void main(String[] args) throws IOException { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); // first BR String fileName = br.readLine(); // read from System.in. br.close(); // close first BR FileReader fr = new FileReader(fileName); // new FR, reading from the filename String. BufferedReader br2 = new BufferedReader(fr); // second BR while (br2.ready()){ String str = br2.readLine(); char[] charArr = str.toCharArray(); for(int i=0; i<charArr.length-1; i++){ char temp = charArr[i]; charArr[i] = charArr[charArr.length -i -1]; charArr[charArr.length -i -1] = temp; } for(char item : charArr){ StringBuilder sb = new StringBuilder(item); System.out.println(sb.reverse()); sb.setLength(0); } } fr.close(); // close filereader br2.close(); // close second BR } }

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Wei Cui

Level 39 , Newark, United States

7 March 2020, 02:19

there is more easier way to solve this problem, Since you try to convert line by line and use BufferedReader. so you can use StringBuilder and it have one methond is called reversed. it will reverse whole line; try this instead line 41 to 55

while(br2.ready()) {
    String line = br2.readLine();
    StringBuilder sb = new StringBuilder(line);  //put all line into StringBuilder
    System.out.println(sb.reverse().toString());  //reverse whole line char by char and print out
}

Anthony Chalk

Level 30 , London, United Kingdom

20 February 2020, 15:32

useful

Problem is in the loop line 44. Say the String was 10 characters long, it would swap the characters like this 1 - 10 2 - 9 3 - 8 etc Except, by the time it's iterated half way through the Array, it's already in reverse order. Therefore, when it iterates over the second half, it's just putting it back in the original order. Either: change it to

for(int i=0; i<charArr.length/2 -1; i++){

or (possibly) simpler

char[] charArr = str.toCharArray();
StringBuilder sb = new StringBuilder();
for (int i = charArr.length - 1; i >= 0; i--){
      sb.append(charArr[i]);
}

Tian Pro

Level 23 , Cape Town, South Africa

24 February 2020, 06:56

Thanks, man. Well explained! For some reason it still doesn't verify though. I've trying a bunch of other stuff but still ain't working! >.<

Tian Pro

Level 23 , Cape Town, South Africa

24 February 2020, 06:58

This is my while and for loops now. Had to rename that other SB as they collided, but I doubt that's the problem haha

while (br2.ready()){
    String str = br2.readLine();
    char[] charArr = str.toCharArray();
    StringBuilder sb = new StringBuilder();
    for (int i = charArr.length - 1; i >= 0; i--){
          sb.append(charArr[i]);
    }

    for(char item : charArr){
        StringBuilder sbItem = new StringBuilder(item);
        System.out.println(sbItem.reverse());
        sbItem.setLength(0);
    }
}

Anthony Chalk

Level 30 , London, United Kingdom

24 February 2020, 09:25

solution

In the loop on line 5 (of your comment) you're reversing the string. So you should just display sb after that loop. There's no need for the loop lines 9-13

Tian Pro

Level 23 , Cape Town, South Africa

25 February 2020, 06:55

Thank you, thank you, THANK YOU! Thanks for your patience with my simple mind haha! I'll go over the material and logic and try figure out the theory so I can do better next time. This helped SO much. :)