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();

java-strings/src/test/java/com/baeldung/string/ReplaceCharInStringUnitTest.java

@@ -1,23 +1,29 @@
 package com.baeldung.string;
 
 import org.junit.Test;
+
 import static org.junit.Assert.*;
 
 public class ReplaceCharInStringUnitTest {
     private ReplaceCharacterInString characterInString = new ReplaceCharacterInString();
 
     @Test
-    public void whenReplaceCharAtIndexUsingSubstring_thenSuccess(){
-        assertEquals("abcme",characterInString.replaceCharSubstring("abcde",'m',3));
+    public void whenReplaceCharAtIndexUsingSubstring_thenSuccess() {
+        assertEquals("abcme", characterInString.replaceCharSubstring("abcde", 'm', 3));
     }
 
     @Test
-    public void whenReplaceCharAtIndexUsingStringBuilder_thenSuccess(){
-        assertEquals("abcme",characterInString.replaceCharStringBuilder("abcde",'m',3));
+    public void whenReplaceCharAtIndexUsingCharArray_thenSuccess() {
+        assertEquals("abcme", characterInString.replaceCharUsingCharArray("abcde", 'm', 3));
     }
 
     @Test
-    public void whenReplaceCharAtIndexUsingStringBuffer_thenSuccess(){
-        assertEquals("abcme",characterInString.replaceCharStringBuffer("abcde",'m',3));
+    public void whenReplaceCharAtIndexUsingStringBuilder_thenSuccess() {
+        assertEquals("abcme", characterInString.replaceCharStringBuilder("abcde", 'm', 3));
+    }
+
+    @Test
+    public void whenReplaceCharAtIndexUsingStringBuffer_thenSuccess() {
+        assertEquals("abcme", characterInString.replaceCharStringBuffer("abcde", 'm', 3));
     }
 }