feat: added code for Dutch national flag algorithm in java

Author: Dipit12

Java/algorithms/sorting/dutchFlagAlgo.java

@@ -0,0 +1,41 @@
+public class DutchFlag {
+
+    public static void sortColors(int[] nums) {
+        int low = 0, mid = 0, high = nums.length - 1;
+
+        while (mid <= high) {
+            switch (nums[mid]) {
+                case 0:
+                    // swap nums[low] and nums[mid]
+                    int temp0 = nums[low];
+                    nums[low] = nums[mid];
+                    nums[mid] = temp0;
+                    low++;
+                    mid++;
+                    break;
+
+                case 1:
+                    mid++;
+                    break;
+
+                case 2:
+                    // swap nums[mid] and nums[high]
+                    int temp2 = nums[mid];
+                    nums[mid] = nums[high];
+                    nums[high] = temp2;
+                    high--;
+                    break;
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        int[] nums = {2, 0, 2, 1, 1, 0};
+        sortColors(nums);
+
+        System.out.print("Sorted array: ");
+        for (int num : nums) {
+            System.out.print(num + " ");
+        }
+    }
+}