Added Character Array method (#5965)

* Added the code of Replace char in a string at specific index

* added test cases

* Renamed the Test class name end with UnitTest

* Renamed the Test class name end with UnitTest

* Renamed the Test class name end with UnitTest

* Replaced README with the upstream repo

* Added Char Array Method

java-strings/src/main/java/com/baeldung/string/ReplaceCharacterInString.java

@@ -1,12 +1,20 @@
 package com.baeldung.string;
 
 public class ReplaceCharacterInString {
-    public  String replaceCharSubstring(String str, char ch, int index) {
-        String myString = str.substring(0, index) + ch + str.substring(index+1);
+
+    public String replaceCharSubstring(String str, char ch, int index) {
+        String myString = str.substring(0, index) + ch + str.substring(index + 1);
         return myString;
     }
 
-    public  String replaceCharStringBuilder(String str, char ch, int index) {
+    public String replaceCharUsingCharArray(String str, char ch, int index) {
+        char[] chars = str.toCharArray();
+        chars[index] = ch;
+        return String.valueOf(chars);
+    }
+
+
+    public String replaceCharStringBuilder(String str, char ch, int index) {
         StringBuilder myString = new StringBuilder(str);
         myString.setCharAt(index, ch);
         return myString.toString();