Saralyn's pull request for Code Review Activity

src/main/java/StringManipulation.java

@@ -1,33 +1,97 @@
 public class StringManipulation implements StringManipulationInterface {
+    private String string;
 
     @Override
     public String getString() {
-        return null;
+        return string;
     }
 
     @Override
     public void setString(String string) {
+        this.string = string;
     }
 
     @Override
     public int count() {
-        return 0;
+        String[] preFilteredResult = string.split(" ");
+        int count = 0;
+
+        for (String result : preFilteredResult) {
+            if (!result.isEmpty()) {
+                count++;
+            }
+        }
+
+        return count;
     }
 
     @Override
     public String removeNthCharacter(int n, boolean maintainSpacing) {
-        return null;
+        if (n <= 0) {
+            throw new IllegalArgumentException();
+        } else if (n > string.length()) {
+            throw new IndexOutOfBoundsException();
+        }
+
+        StringBuilder stringBuilder = new StringBuilder();
+
+        for (int i = 0; i < string.length(); i++) {
+            if ((i + 1) % n == 0) {
+                if (maintainSpacing) {
+                    stringBuilder.append(" ");
+                }
+            } else {
+                stringBuilder.append(string.charAt(i));
+            }
+        }
+
+        return stringBuilder.toString();
     }
 
     @Override
-    public String[] getSubStrings(int startWord, int endWord) {
-        return null;
+    public String[] getSubStrings(int startWord, int endWord){
+        if (startWord <= 0 || endWord <= 0 || startWord > endWord) {
+            throw new IllegalArgumentException();
+        }
+
+        String[] preFilteredResult = string.split(" ");
+        String[] substrings = new String[endWord - startWord + 1];
+        int wordCount = 1;
+        int substringsIndex = 0;
+
+        for (String result : preFilteredResult) {
+            if (!result.isEmpty()) {
+                if (wordCount >= startWord && wordCount <= endWord) {
+                    substrings[substringsIndex] = result;
+                    substringsIndex++;
+                }
+                wordCount++;
+            }
+        }
+
+        if (wordCount < endWord) {
+            throw new IndexOutOfBoundsException();
+        }
+
+        return substrings;
     }
 
     @Override
-    public String restoreString(int[] indices) {
-        return null;
-    }
+    public String restoreString(int[] indices){
+        if (indices.length != string.length()) {
+            throw new IllegalArgumentException();
+        }
 
+        String[] restoredStringArray = new String[indices.length];
 
+        for (int i = 0; i < indices.length; i++) {
+            int oldIndex = indices[i];
+            if (oldIndex < 0 || oldIndex >= string.length()) {
+                throw new IndexOutOfBoundsException();
+            }
+            restoredStringArray[i] = String.valueOf(string.charAt(oldIndex));
+        }
+
+        return String.join("", restoredStringArray);
+    }
 }