Hen java collections completed

src/main/java/Collections/Practice/CollectionBasics.java

@@ -33,6 +33,9 @@ public static int sum(Collection<Integer> numbers) {
         // TODO:
         // Loop through the collection
         // Add each number to total
+        for(Integer number : numbers){
+            total+= number;
+        }
 
         return total;
     }
@@ -49,6 +52,11 @@ public static int countEven(Collection<Integer> numbers) {
         // TODO:
         // Loop through the collection
         // If the number is even, increase count
+        for(Integer number : numbers){
+            if(number % 2 == 0){
+                count ++;
+            }
+        }
 
         return count;
     }
@@ -65,6 +73,9 @@ public static int findMax(Collection<Integer> numbers) {
         // TODO:
         // Loop through numbers
         // Update max if current number is larger
+        for (Integer number : numbers){
+            max = Math.max(max,number);
+        }
 
         return max;
     }
@@ -80,24 +91,42 @@ public static boolean hasDuplicates(Collection<Integer> numbers) {
         // TODO:
         // Hint:
         // Compare the size of a collection with the size of a Set
+        for (Integer a : numbers) {
+            int count = 0;
+
+            for (Integer b : numbers) {
+                if (a.equals(b)) {
+                    count++;
+                }
+
+                if (count > 1) {
+                    return true;
+                }
+            }
+        }
 
         return false;
     }
 
-
     /*
      PROBLEM 5
      Count how many times a target value appears
     */
     public static int countOccurrences(Collection<Integer> numbers, int target) {
 
         int count = 0;
-
+        for (Integer a : numbers) {
+                if (a.equals(target)) {
+                    count++;
+            }
+            return count;
+        }
         // TODO:
         // Loop through numbers
         // If number equals target, increase count
 
         return count;
+
     }
 
 

src/main/java/Collections/Practice/CommonMethodsDemo.java

@@ -131,40 +131,70 @@ public static void main(String[] args) {
          Add the following values:
          10, 20, 30, 40, 50
         */
+        Collection<Integer> numbers = new ArrayList<>();
+        numbers.add(10);
+        numbers.add(20);
+        numbers.add(30);
+        numbers.add(40);
+        numbers.add(50);
+        System.out.println(numbers);
 
 
         /*
          TODO 2:
          Print the size of the numbers collection
         */
 
+        System.out.println("Size collection: "+ numbers.size());
 
         /*
          TODO 3:
          Check if the collection contains 30
         */
-
+        for (Integer number: numbers){
+            if(numbers.contains(30)){
+                System.out.println(true);
+                break;
+            }
+        }
 
         /*
          TODO 4:
          Remove the number 20
         */
+        numbers.remove(20);
+        System.out.println(numbers);
 
 
         /*
          TODO 5:
          Loop through the numbers collection
          and print each value
         */
+        for(Integer number: numbers){
+            System.out.println(number);
+        }
 
 
         /*
          REFLECTION QUESTIONS:
 
          1. Why can we use Collection as the reference type?
+
+         - Interface Parent class of data structures such as lists, sets,
+         and queues.
+
          2. What methods are available because of the Collection interface?
+
+         - add(), remove(), size(), isEmpty();, contains(), iterator(), clear()
+
          3. What methods are NOT available when using Collection instead of List?
+
+         - get(int index), set(int index, element), add(int index, element),
+         remove(int index)
+
          */
+
     }
 
 }