diff --git a/SllidingWindow.java b/SllidingWindow.java
new file mode 100644
index 000000000000..592eaf63acca
--- /dev/null
+++ b/SllidingWindow.java
@@ -0,0 +1,77 @@
+// 1st question using sliding window technique
+// 1st 
+// MAXIMUM SUM SUB ARRAY OF SIZE K : using sliding window technique
+class GFG {
+    // Returns maximum sum in
+    // a subarray of size k.
+    static int maxSum(int arr[], int n, int k)
+    {
+        // Initialize result
+        int max_sum = Integer.MIN_VALUE;
+
+        // Consider all blocks starting with i.
+        for (int i = 0; i < n - k + 1; i++) {
+            int current_sum = 0;
+            for (int j = 0; j < k; j++)
+                current_sum = current_sum + arr[i + j];
+
+            // Update result if required.
+            max_sum = Math.max(current_sum, max_sum);
+        }
+
+        return max_sum;
+    }
+
+    // Driver code
+    public static void main(String[] args)
+    {
+        int arr[] = { 1, 4, 2, 10, 2, 3, 1, 0, 20 };
+        int k = 4;
+        int n = arr.length;
+        System.out.println(maxSum(arr, n, k));
+    }
+}
+
+// 2nd question using sliding window technique
+// 2nd
+// Longest Substring Without Repeating Characters: using sliding window technique
+import java.util.*;
+
+public class GfG {
+    
+    // Function to find the length of the longest 
+      // substring without repeating characters
+    static int longestUniqueSubstr(String s) {
+        int n = s.length();
+        int res = 0;
+
+        for (int i = 0; i < n; i++) {
+
+            // Initializing all characters as not visited
+            boolean[] visited = new boolean[256];
+
+            for (int j = i; j < n; j++) {
+
+                // If current character is visited, 
+                  // Break the loop
+                if (visited[s.charAt(j)]) {
+                    break;
+                } 
+                  else {
+                  
+                    // Else update the result if this 
+                    // window is larger, and mark current 
+                      // character as visited.
+                    res = Math.max(res, j - i + 1);
+                    visited[s.charAt(j)] = true;
+                }
+            }
+        }
+        return res;
+    }
+
+    public static void main(String[] args) {
+        String s = "geeksforgeeks";
+        System.out.println(longestUniqueSubstr(s));
+    }
+}