diff --git a/src/main/java/io/zipcoder/Problem1.java b/src/main/java/io/zipcoder/Problem1.java
index 6cd6024..a825a0b 100644
--- a/src/main/java/io/zipcoder/Problem1.java
+++ b/src/main/java/io/zipcoder/Problem1.java
@@ -1,4 +1,48 @@
 package io.zipcoder;
 
+import java.util.HashMap;
+import java.util.Map;
+
 public class Problem1 {
+
+    public Map<Character, Character> getMap(){
+        Map<Character, Character> substitutionMap=new HashMap<Character, Character>();
+        substitutionMap.put('f','7');
+        substitutionMap.put('s', '$');
+        substitutionMap.put('1','!');
+        substitutionMap.put('a','@');
+        return substitutionMap;
+    }
+
+    public Character subInLetter(char letter){
+        Map<Character,Character> substitutionMap=getMap();
+
+        Character newLetter=substitutionMap.get(letter);
+        if(newLetter!=null)
+            return newLetter;
+        else return letter;
+    }
+
+    public String replaceSentence(String sentence){
+        StringBuilder replacedSentence=new StringBuilder();
+
+
+        for(int i=0; i<sentence.length(); i++){
+            Character letter=sentence.toLowerCase().charAt(i);
+            letter=subInLetter(letter);
+            if(letter!=sentence.toLowerCase().charAt(i))
+                replacedSentence.append(letter);
+            else replacedSentence.append(sentence.charAt(i));
+        }
+        return replacedSentence.toString();
+    }
+
+    public String replacementRecurrsion(String sentence, Integer index ){
+        Map<Character, Character> substitutionMap=getMap();
+
+
+//        replacementRecurrsion()
+        return null;
+    }
+
 }
diff --git a/src/test/java/io/zipcoder/Problem1Test.java b/src/test/java/io/zipcoder/Problem1Test.java
index de82e99..d2666f3 100644
--- a/src/test/java/io/zipcoder/Problem1Test.java
+++ b/src/test/java/io/zipcoder/Problem1Test.java
@@ -1,4 +1,38 @@
 package io.zipcoder;
 
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
 public class Problem1Test {
+    Problem1 problem1=new Problem1();
+
+    @Test
+    public void createMapTest(){
+        Character expected='@';
+        Character actual=problem1.subInLetter('a');
+
+        Assert.assertEquals(expected,actual);
+    }
+
+    @Test
+    public void createMapTest2(){
+        Character expected='t';
+        Character actual=problem1.subInLetter('t');
+
+        Assert.assertEquals(expected,actual);
+    }
+
+    @Test
+    public void replaceSentenceTest(){
+        String given="The Farmer went to the store to get 1 dollar’s worth of fertilizer";
+        String expected="The 7@rmer went to the $tore to get ! doll@r’$ worth of 7ertilizer";
+        String actual = problem1.replaceSentence(given);
+
+        Assert.assertEquals(expected,actual);
+
+    }
 }
+