Added solution for Trapping Rain water problem in java

Author: kunal164107

Trapping Rain Water.java

@@ -0,0 +1,49 @@
+// Java program to find maximum amount of water that can 
+// be trapped within given set of bars. 
+  
+class Test 
+{ 
+    static int arr[] = new int[]{0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1}; 
+      
+    // Method for maximum amount of water 
+    static int findWater(int n) 
+    { 
+        // left[i] contains height of tallest bar to the 
+        // left of i'th bar including itself 
+        int left[] = new int[n]; 
+       
+        // Right [i] contains height of tallest bar to 
+        // the right of ith bar including itself 
+        int right[] = new int[n]; 
+       
+        // Initialize result 
+        int water = 0; 
+       
+        // Fill left array 
+        left[0] = arr[0]; 
+        for (int i = 1; i < n; i++) 
+           left[i] = Math.max(left[i-1], arr[i]); 
+       
+        // Fill right array 
+        right[n-1] = arr[n-1]; 
+        for (int i = n-2; i >= 0; i--) 
+           right[i] = Math.max(right[i+1], arr[i]); 
+       
+        // Calculate the accumulated water element by element 
+        // consider the amount of water on i'th bar, the 
+        // amount of water accumulated on this particular 
+        // bar will be equal to min(left[i], right[i]) - arr[i] . 
+        for (int i = 0; i < n; i++) 
+           water += Math.min(left[i],right[i]) - arr[i]; 
+       
+        return water; 
+    } 
+      
+    // Driver method to test the above function 
+    public static void main(String[] args)  
+    { 
+          
+        System.out.println("Maximum water that can be accumulated is " +  
+                                        findWater(arr.length)); 
+    } 
+}