diff --git a/correct_parenthesis.java b/correct_parenthesis.java
new file mode 100644
index 0000000..26e9502
--- /dev/null
+++ b/correct_parenthesis.java
@@ -0,0 +1,18 @@
+import java.util.*;
+class Solution {
+    boolean solution(String s) {
+        boolean answer = true;
+        Deque<Character> parenthesis = new ArrayDeque<>();
+        Map<Character,Character> pair = Map.of(')','(');
+        for(char c : s.toCharArray()){
+            if(c=='('){
+                parenthesis.push(c);
+            }else{
+                if(parenthesis.isEmpty() || pair.get(c)!=parenthesis.pop()){
+                    return false;
+                }
+            }
+        }
+        return parenthesis.isEmpty();
+    }
+}
diff --git a/no_completion.java b/no_completion.java
new file mode 100644
index 0000000..ce7991c
--- /dev/null
+++ b/no_completion.java
@@ -0,0 +1,14 @@
+import java.util.*;
+class Solution {
+    public String solution(String[] participant, String[] completion) {
+        Arrays.sort(participant);
+        Arrays.sort(completion);
+        int i;
+        for(i=0; i<completion.length;i++){
+            if(!participant[i].equals(completion[i])){
+                return participant[i];
+            }
+        }
+        return participant[i];
+    }
+}