diff --git a/src/main/java/StringManipulation.java b/src/main/java/StringManipulation.java
index 4deb6f1..75e1038 100644
--- a/src/main/java/StringManipulation.java
+++ b/src/main/java/StringManipulation.java
@@ -1,33 +1,120 @@
 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;
+
+        if (this.string == null){
+            throw new NullPointerException("NullPointerException");
+        }
+
+        if (this.string.isEmpty()){
+            return 0;
+        }
+
+        String[] result = this.string.split("\s+");
+        int word = 0;
+        for (String current : result) {
+            if (!current.isEmpty()) {
+                word++;
+            }
+        }
+        return word;
     }
 
     @Override
     public String removeNthCharacter(int n, boolean maintainSpacing) {
-        return null;
+
+        if (this.string == null || this.string.isEmpty()){
+            throw new NullPointerException("NullPointerException");
+        }
+        int length = string.length();
+
+        if (n > string.length()) {
+            throw new IndexOutOfBoundsException("Out Of Bound");
+//            System.out.println("Out Of Bound");
+        }
+
+        if (n <= 0) {
+            throw new IllegalArgumentException("Invalid");
+        }
+
+        StringBuilder result = new StringBuilder();
+
+        for (int index = 0; index < length; index++) {
+            int compare = index + 1;
+
+            if (compare % n != 0) {
+                result.append(string.charAt(index));
+
+            } else if (maintainSpacing == true) {
+                result.append(' ');
+            }
+        }
+        return result.toString();
     }
 
     @Override
     public String[] getSubStrings(int startWord, int endWord) {
-        return null;
+        if (startWord <= 0 || endWord <= 0 || startWord > endWord) {
+            throw new IllegalArgumentException("Invalid startWord or endWord");
+        }
+        //String sentence = "This is an example sentence";
+        String[] words = this.string.split(" ");
+
+        if (endWord > words.length) {
+            throw new IndexOutOfBoundsException("Not enough words in the sentence");
+        }
+
+        String[] subStrings = new String[endWord - startWord + 1];
+        int index = 0;
+
+        for (int i = startWord - 1; i < endWord; i++) {
+            subStrings[index] = words[i];
+            index++;
+        }
+
+        return subStrings;
     }
 
+
     @Override
     public String restoreString(int[] indices) {
-        return null;
-    }
+        if (this.string.isEmpty()){
+            return "";
+        }
+
+        if ( indices.length != string.length()) {
+            throw new IllegalArgumentException("Invalid");
+        }
 
+        if (string == null || indices == null) {
+            throw new NullPointerException("NullPointerException");
+        }
+
+        char[] restoredChars = new char[string.length()];
+
+        for (int i = 0; i < indices.length; i++) {
+            int index = indices[i];
+            if (index < 0 || index >= string.length()) {
+                throw new IndexOutOfBoundsException("Not enough words in the sentence");
+            }
+            restoredChars[index] = string.charAt(i);
+        }
+
+        return new String(restoredChars);
+    }
 
 }
+
diff --git a/src/main/java/StringManipulationInterface.java b/src/main/java/StringManipulationInterface.java
index 87127e7..cc81e80 100644
--- a/src/main/java/StringManipulationInterface.java
+++ b/src/main/java/StringManipulationInterface.java
@@ -79,10 +79,10 @@ public interface StringManipulationInterface {
      * The string s will be shuffled such that the character at the ith position moves to indices[i] in the shuffled string.
      * Return the shuffled string.
      * example:
-     * Input: string = "UnitTest", indices = [4,5,6,7,0,1,2,3]
+     * Input: string = "UnitTest", indices = [4,5,6,7,0,2,1,3]
      * Output: "TestUnit"
      * Explanation:
-     * indices: 4 5 6 7 0 1 2 3
+     * indices: 4 5 6 7 0 2 1 3
      * String:  U n i t T e s t
      * Actions to Shuffle: Shift U to 4th position, n to 5th position, i to 6th position ......
      * Output: T e s t U n i t
@@ -95,7 +95,7 @@ public interface StringManipulationInterface {
      * indices length is the same as the string length.
      *
      * throws IllegalArgumentException if not s.length == indices.length == n
-     * throws IndexOutOfBoundsException if   indices[i]< 0  or  indices[i]>= string length
+     * throws IndexOutOfBoundsException if   indices[i]< 0  or  indices[i]> string length
      *
      * @param indices is an integer array for shuffled string new indices positions
      * the character at the ith position moves to indices[i] in the shuffled string.
diff --git a/src/test/java/StringManipulationTest.java b/src/test/java/StringManipulationTest.java
index 6692c2c..2d18e98 100644
--- a/src/test/java/StringManipulationTest.java
+++ b/src/test/java/StringManipulationTest.java
@@ -1,3 +1,4 @@
+import jdk.jfr.StackTrace;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -28,17 +29,30 @@ public void testCount1() {
 
     @Test
     public void testCount2() {
-        fail("Not yet implemented");
+        manipulatedstring.setString("");
+        int length = manipulatedstring.count();
+        assertEquals(0, length);
     }
 
     @Test
     public void testCount3() {
-        fail("Not yet implemented");
+        assertThrows(NullPointerException.class, () -> {
+            //int length = 
+            manipulatedstring.count();
+        });
     }
 
     @Test
     public void testCount4() {
-        fail("Not yet implemented");
+        manipulatedstring.setString("Spaces   between  words ");
+        int length = manipulatedstring.count();
+        assertEquals(3, length);
+    }
+
+    public void testCount5() {
+        manipulatedstring.setString(" ABCDEFD ");
+        int length = manipulatedstring.count();
+        assertEquals(1, length);
     }
 
     @Test
@@ -52,32 +66,49 @@ public void testRemoveNthCharacter2() {
         manipulatedstring.setString("I'd b3tt3r put s0me d161ts in this 5tr1n6, right?");
         assertEquals("I'  b tt r  ut s0 e  16 ts in th s  tr n6  r gh ?", manipulatedstring.removeNthCharacter(3, true));
     }
-
     @Test
     public void testRemoveNthCharacter3() {
-        fail("Not yet implemented");
+        //null
+        assertThrows(NullPointerException.class,() ->{
+            manipulatedstring.removeNthCharacter(3, true);
+        });
     }
 
+
     @Test
-    public void testRemoveNthCharacter4() {
-        fail("Not yet implemented");
+    public void testRemoveNthCharacter4(){
+        assertThrows(IllegalArgumentException.class, () -> {
+            manipulatedstring.setString("BUBU");
+            manipulatedstring.removeNthCharacter(-3, true);
+        });
     }
 
     @Test
-    public void testRemoveNthCharacter5() {
-        fail("Not yet implemented");
+    public void testRemoveNthCharacter5(){
+        assertThrows(IndexOutOfBoundsException.class, () -> {
+            manipulatedstring.setString("love");
+            manipulatedstring.removeNthCharacter(7, true);
+        });
     }
 
     @Test
-    public void testRemoveNthCharacter6() {
-        fail("Not yet implemented");
+    public void testRemoveNthCharacter6(){
+        assertThrows(IllegalArgumentException.class, () -> {
+            manipulatedstring.setString(" ");
+            manipulatedstring.removeNthCharacter(0, true);
+        });
     }
 
     @Test
-    public void testRemoveNthCharacter7() {
-        fail("Not yet implemented");
+    public void testRemoveNthCharacter7(){
+        assertThrows(NullPointerException.class, () -> {
+            manipulatedstring.setString(""); //empty
+            manipulatedstring.removeNthCharacter(0,true);
+
+        });
     }
 
+
     @Test
     public void testGeSubStrings1() {
         manipulatedstring.setString("This is my string");
@@ -88,26 +119,42 @@ public void testGeSubStrings1() {
     }
 
     @Test
-    public void testGeSubStrings2() {
-        fail("Not yet implemented");
-    }
-    @Test
-    public void testGeSubStrings3() {
-        fail("Not yet implemented");
+    public void testGetSubStrings2() {
+        assertThrows(IllegalArgumentException.class, () -> {
+            manipulatedstring.setString("OnlyOneWord");
+           // String[] subStrings = 
+           manipulatedstring.getSubStrings(1, -1);
+        });
     }
+
     @Test
-    public void testGeSubStrings4() {
-        fail("Not yet implemented");
+    public void testGetSubStrings3() {
+        assertThrows(IndexOutOfBoundsException.class, () -> {
+            manipulatedstring.setString("One Two Three Four Five");
+            String[] subStrings = manipulatedstring.getSubStrings(4, 6);
+
+            assertEquals("Four", subStrings[0]);
+            assertEquals("Five", subStrings[1]);
+        });
     }
+
     @Test
-    public void testGeSubStrings5() {
-        fail("Not yet implemented");
+    public void testGetSubStrings4() {
+        assertThrows(IllegalArgumentException.class, () -> {
+            manipulatedstring.setString("One Two Three Four Five");
+            String[] subStrings = manipulatedstring.getSubStrings(50,1);
+        });
     }
+
     @Test
-    public void testGeSubStrings6() {
-        fail("Not yet implemented");
+    public void testGetSubString5() {
+        assertThrows(IllegalArgumentException.class, () -> {
+            manipulatedstring.setString("Programming");
+            String[] subStrings = manipulatedstring.getSubStrings(0, 0);
+        });
     }
 
+
     @Test
     public void testRestoreString1()
     {
@@ -119,31 +166,42 @@ public void testRestoreString1()
     }
 
     @Test
-    public void testRestoreString2()
-    {
-        fail("Not yet implemented");
-
+    public void testRestoreString2() {
+        assertThrows(IllegalArgumentException.class, () -> {
+            manipulatedstring.setString("testing");
+            int[] indices = {};
+            //String restoredString = 
+            manipulatedstring.restoreString(indices);
+        });
     }
 
     @Test
-    public void testRestoreString3()
-    {
-        fail("Not yet implemented");
-
+    public void testRestoreString3() {
+        assertThrows(NullPointerException.class,() ->{
+            int[] indices = {};
+            //String restoredString = 
+            manipulatedstring.restoreString(indices);
+        });
     }
 
     @Test
-    public void testRestoreString4()
-    {
-        fail("Not yet implemented");
-
+    public void testRestoreString4() {
+        assertThrows(IndexOutOfBoundsException.class, () -> {
+            manipulatedstring.setString("hello");
+            int[] indices = {4, 3, 2, 1, -1};
+           // String restoredString = 
+           manipulatedstring.restoreString(indices);
+        });
     }
 
     @Test
-    public void testRestoreString5()
-    {
-        fail("Not yet implemented");
-
+    public void testRestoreString5() {
+        assertThrows(IndexOutOfBoundsException.class, () -> {
+            manipulatedstring.setString("world");
+            int[] indices = {0, 2, 1, 3, 5};
+            //String restoredString = 
+            manipulatedstring.restoreString(indices);
+        });
     }
 
 }