diff --git a/Array/Easy/Letter Combinations_of_a_Phone_Number.java b/Array/Easy/Letter Combinations_of_a_Phone_Number.java
new file mode 100644
index 0000000..cddcbd7
--- /dev/null
+++ b/Array/Easy/Letter Combinations_of_a_Phone_Number.java	
@@ -0,0 +1,34 @@
+class Solution {
+    public List<String> letterHelper(String digit,HashMap<Character,String> map){
+        if(digit.equals("")) return new ArrayList<String> (0);
+        if(digit.length() == 1){
+            List<String> list = new ArrayList<>(3);
+            String s = map.get(digit.charAt(0));
+            for(int i = 0;i<s.length();i++){
+                list.add(String.valueOf(s.charAt(i)));
+            }
+            return list;
+        }
+        List<String> list = letterHelper(digit.substring(1,digit.length()),map);
+        List<String> result = new ArrayList<>();
+        String s = map.get(digit.charAt(0));
+        for(int i = 0;i<s.length();i++){
+            for(int j = 0;j<list.size();j++){
+                result.add(String.valueOf(s.charAt(i)).concat(list.get(j)) );
+            }
+        }
+        return result;
+    }
+    public List<String> letterCombinations(String digits) {
+        HashMap<Character,String> map = new HashMap<>(8);
+        map.put('2',"abc");
+        map.put('3',"def");
+        map.put('4',"ghi");
+        map.put('5',"jkl");
+        map.put('6',"mno");
+        map.put('7',"pqrs");
+        map.put('8',"tuv");
+        map.put('9',"wxyz");
+        return letterHelper(digits,map);
+    }
+}
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