added my implementation to skeleton

src/main/java/StringManipulation.java

@@ -1,4 +1,5 @@
 public class StringManipulation implements StringManipulationInterface {
+    private String myString;
 
     @Override
     public String getString() {
@@ -7,27 +8,120 @@ public String getString() {
 
     @Override
     public void setString(String string) {
+        this.myString = string;
     }
 
     @Override
     public int count() {
-        return 0;
+        if(myString == null){
+            return 0;
+        }
+
+        int countWords = 0;
+        if(myString.equals("")){
+            return countWords;
+        }
+
+        String removeSpace = myString.trim();
+        for(String word : removeSpace.split("\\s+")){
+            if(removeSpace.equals(""))
+                return 0;
+            countWords++;
+        }
+
+        return countWords;
     }
 
     @Override
     public String removeNthCharacter(int n, boolean maintainSpacing) {
-        return null;
+        if (myString.equals("")) {
+            return myString;
+        } else if(myString == null){
+            throw new NullPointerException("String is null.");
+        } else if(n <= 0){
+            throw new IllegalArgumentException("n cannot be less than or equal to zero");
+        } else if(n > myString.length()){
+            throw new IndexOutOfBoundsException("n cannot be greater than string length");
+        } else if(n == 1 && maintainSpacing){
+            return myString;
+        }
+
+        StringBuilder result = new StringBuilder();
+        int count = 0;
+
+        for (int i = 0; i < myString.length(); i++) {
+            char c = myString.charAt(i);
+
+            if (maintainSpacing) {
+                count++;
+
+                if (count % n != 0) {
+                    result.append(c);
+                } else {
+                    result.append(' ');
+                }
+            } else {
+                count++;
+                if (count % n != 0) {
+                    result.append(c);
+                }
+            }
+        }
+        return result.toString();
     }
 
     @Override
-    public String[] getSubStrings(int startWord, int endWord) {
-        return null;
+    public String[] getSubStrings(int startWord, int endWord){
+        if(myString == null) {
+            throw new NullPointerException("String is null.");
+        } else if(startWord > endWord){
+            throw new IllegalArgumentException("startWord cannot be greater than endWord.");
+        } else if(startWord <= 0){
+            throw new IllegalArgumentException("startWord cannot be less than or equal to 0.");
+        } else if(endWord <= 0){
+            throw new IllegalArgumentException("endWord cannot be less than or equal to 0.");
+        }
+
+        //handles exception for endWord># of words in string
+        String[] words = myString.split("\\s+");
+        if(endWord > words.length){
+            throw new IndexOutOfBoundsException("endWord is greater than length of string.");
+        }
+
+        int size = endWord - startWord + 1;
+        String[] result = new String[size];
+        int index = 0;
+
+        for (int i = startWord-1; i < endWord; i++) {
+            result[index] = words[i];
+            index++;
+        }
+
+        return result;
     }
 
     @Override
-    public String restoreString(int[] indices) {
-        return null;
-    }
+    public String restoreString(int[] indices){
+        if(indices.length != myString.length()){
+            throw new IllegalArgumentException("Indices length does not equal string's length");
+        } else if(myString == null){
+            throw new NullPointerException("String is null.");
+        }
 
+        StringBuilder result = new StringBuilder(myString.length());
+
+        for(int index : indices){
+
+            if(index < 0 || index > myString.length()){
+                throw new IndexOutOfBoundsException("Indices length cannot be less than 0");
+            } else if(myString.equals("")){
+                return result.toString();
+            } else {
+                result.append(myString.charAt(index));
+            }
+        }
+
+        return result.toString();
+    }
 
 }