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Why is it throwing an error? Any help would be appreciated

public class RAWS {public String rawsc(String ori){    String temp="";    for(int i=0;i<ori.length();i++)    {        char c=ori.charAt(i);        if(((c>=65)&&(c<=90))||((c>=97)&&(c<122)))            temp=c+temp;    }    for(int i=0;i<ori.length();i++)    {        char c=ori.charAt(i);        if(((c>=65)&&(c<=90))||((c>=97)&&(c<122)))            ori.replace(c, temp.charAt(i));    }    for(int i=0;i<ori.length();i++)    {        System.out.println(ori.charAt(i));    }    return(ori);}public static void main(String[] args) {    String str="a,b$c";    RAWS ob=new RAWS();    String new1=ob.rawsc(str);    for(int i=0;i<new1.length();i++)    {        System.out.print(new1.charAt(i)+" ");    }}}

Editor:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 4 at java.lang.String.charAt(String.java:658) at arraygs.RAWS.rawsc(RAWS.java:22) at arraygs.RAWS.main(RAWS.java:30)

Here is some Java code to reverse a string recursively.

Could someone provide an explanation of how it works?

public static String reverse(String str) {    if ((null == str) || (str.length() <= 1)) {        return str;    }    return reverse(str.substring(1)) + str.charAt(0);}

I'm not understanding how this can possibly work.

I have a alphabet string like:

string = 'abcdefghijklmnopqrstuvwxyz'

if want to do slicing and and go from z to a but with 3 steps. what should I do? I know string[::-1] will reverse it but how can I make it go by 3 steps each time?

I have done it by assigning a new string which is reverse of the other string and do slicing with 3 steps from there. I'm looking for a new way to do it without changing the previous string and doing it on the same spot

I'm completely new to coding and have been recommended to try Ruby.There is a practice test for an internship that asks to write a function that returns the reverse, without using the built-in reverse function.I have tried multiple different solutions that I followed from youtube/stack overflow and some medium blog posts and all of them return 'inconclusive'

Can anyone explain what is wrong with the code I wrote, and how it diverges from what is expected by the tests?

I already tried the code below.

def string_reverse(input)    split_string = string.split("")    reversed = []    string.size.times { reversed << split_string.pop }    reversed.joinendputs string_reverse("Hello")

This is what is in the test window:

require './solution'require 'minitest/autorun'class TestSolution < MiniTest::Unit::TestCasedef test_1    assert_equal "olleH", string_reverse("Hello")enddef test_2    assert_equal "A", string_reverse("A")enddef test_3    assert_equal "", string_reverse("")endend

This is what was in the output window:

/sandboxes/hyena/solution.rb:2:in `string_reverse': undefined local variable or method `string' for main:Object (NameError)Did you mean?  String    from /sandboxes/hyena/solution.rb:8:in `<top (required)>'    from /usr/local/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'    from /usr/local/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'    from test_solution.rb:1:in `<main>'

I am currently getting my head around recursion in Java. Having come across the below code, I can't work out how the recursive method produces the reverse String. Any explanation would be appreciated!

class Backwards {    String str;    Backwards(String s) {        str = s;    }    void backward(int idx) {        if(idx != str.length()-1) {            backward(idx+1);        }        System.out.print(str.charAt(idx));    }}

class BWDemo {    public static void main(String args[]) {        Backwards s = new Backwards("This is a test");        s.backward(0);    }}