CODEWITHSUNDEEP
javajava.util.scannerreverse
com9
com9

Reputation: 43

How do I reverse all Strings in my array?

How do I reverse my array output? Like "peter" to "retep" or "max" to "xam"

I tried to use collections but it's not working

This is my code:

import java.util.Scanner;
import java.util.Collections;

public class sdf {

    public static void main (String[] args) {
        Scanner input = new Scanner(System.in);
        String[] my_friend_names = new String[10];

        for (int i = 0; i < my_friend_names.length; i++) {
            my_friend_names[i] = input.nextLine();
        }
        for(int i = 0; i < my_friend_names.length; i++) {
            System.out.println("Name: " + my_friend_names[i]);
        }

        Collections.reverse(input);
        System.out.println("After Reverse order: " +input);
    }

}

Upvotes: 2

Views: 831

Answers (4)

McLovin
McLovin

Reputation: 1601

You are trying to print out input which is of type Scanner. Try using StringBuilder

Scanner input = new Scanner(System.in);
String[] my_friend_names = new String[10];

for (int i = 0; i < my_friend_names.length; i++) {
    my_friend_names[i] = input.nextLine();

    String reversedName =  new StringBuilder(my_friend_names[i]).reverse().toString();
    System.out.println("After reverse: " + reversedName);
}

Upvotes: 0

Guy Nachimson
Guy Nachimson

Reputation: 31

Seems you create a string array, but than proceed to try reverse the input. If you want to use collections you may do something like this:

    List<String> list = Arrays.asList(my_friend_names);
    Collections.reverse(list);
    System.out.println("After Reverse order: " + list);

Upvotes: 3

Charlie
Charlie

Reputation: 986

I think it would be the best way to make a char[] from the String, reverse that char[] and convert it back to a String.

Something like this should do the job:

    Scanner input = new Scanner(System.in);
    String[] my_friend_names = new String[10];

    for (int i = 0; i < my_friend_names.length; i++) {
        my_friend_names[i] = input.nextLine();
    }

    input.close();

    for(String name : my_friend_names) {
        System.out.println("Name: " + name);
    }

    for(int i=0; i<my_friend_names.length; i++) {
        char[] characters=my_friend_names[i].toCharArray();
        List<char[]> reverse=Arrays.asList(characters);
        Collections.reverse(reverse);
        my_friend_names[i]=new String(characters);
    }

    System.out.println("After Reverse order: ");

    for(String name : my_friend_names) {
        System.out.println("Name: " + name);
    }

Let me know whether it works (or not)
Happy coding :) -Charlie

Upvotes: 0

Adam
Adam

Reputation: 36703

Your posted code does not compile, for example you call Collections.reverse() on your scanner variable.

Things that might help you.

  • You've assumed Collections.reverse() will reverse the Strings within the array - it won't, it simply reverses the order of the Strings, e.g.
  • Collections.reverse() works on java.util.List not a primitive array, you can use Arrays.toList() if you need it
  • StringBuilder provides a handle reverse() method

Example, use StringBuilder.reverse() to update replace each item in the array with a reversed String

String[] my_friend_names = { "fred", "alice" };

for (int i = 0; i < my_friend_names.length; i++) {
    my_friend_names[i] = new StringBuilder(my_friend_names[i])
            .reverse().toString();
}

System.out.println(Arrays.toString(my_friend_names));

Output

[derf, ecila]

Upvotes: 1

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