added Array list based program by java

data_structures/arraylist/java/Find_Frequency_Element_Array.java

@@ -0,0 +1,39 @@
+/**
+ * find the frequency of element in arry; 
+ *  arr = {2,33,4,4,54,3,2}
+ * 
+ * output : 
+ * 2 ->2
+ * 33->1
+ * 4->2
+ * 54->1
+ * 3->1
+ */
+
+
+import java.util.HashMap;
+import java.util.IdentityHashMap;
+import java.util.Map;
+
+public class FrequencyOfEachElementArray {
+   public  static  void  PrintFri(int arr[]){
+       Map<Integer , Integer> map = new HashMap<>();
+
+       for (int i = 0; i < arr.length; i++) {
+           if(map.containsKey(arr[i])){
+               map.put(arr[i], map.get(arr[i]) + 1);
+           }
+           else {
+               map.put(arr[i], 1);
+           }
+       }
+
+       for(Map.Entry<Integer, Integer>  entry:  map.entrySet()){
+           System.out.println(entry.getKey() + " " + entry.getValue());
+       }
+   }
+    public static void main(String[] args) {
+        int arr[] = {21,2,4,56,5,3,2,3,2,34,};
+        PrintFri(arr);
+    }
+}

data_structures/arraylist/java/Find_Second_Largest_Number_In_Array.java

@@ -0,0 +1,37 @@
+import java.util.Arrays;
+
+/**
+ * To find second highest number form the array :
+ * example :
+ * arr = { 23,45,65,4,6,7}
+ * output : 45
+ * */
+public class SecondHighestNumberInArray {
+    //functin
+    public  static  void SecondLargestNum(int arr[]){
+        int size = arr.length;
+        if(size<2){
+            System.out.println("Invalid input ");
+            return;
+        }
+        Arrays.sort(arr);
+        System.out.println(arr[size-2]);
+        for(int i= size-2; i>=0; i--){
+            if(arr[i]!=arr[size-1]) {
+                System.out.println(arr[i]);
+                return;
+            }
+
+        }
+        System.out.println("There are no largest number ");
+    }
+    public static void main(String[] args) {
+        int arr[] = {4,4,4,4,4,4,4,4,4};
+        //object of class
+        SecondHighestNumberInArray secondHigh = new SecondHighestNumberInArray();
+        secondHigh.SecondLargestNum(arr);
+
+    }
+}
+
+//output : there are no largest numebr