eg change order

Week 3: Objects, files and exceptions/5a. Method side effects

@@ -0,0 +1,51 @@
+Avoid changing input object in a method
+
+eg
+ordering the list by size using the sort method in the Collections class:
+public static int secondSmallest(ArrayList<Integer> numbers) {
+    Collections.sort(numbers);
+    return (numbers.get(1));
+}
+
+
+
+
+The method itself does produce the correct result, but it also AFFECTS the ORDER of the list:
+
+import java.util.ArrayList;
+import java.util.Collections;
+
+public class Example {
+    public static void main(String[] args){
+        ArrayList<Integer> numbers = new ArrayList<>();
+        numbers.add(5);
+        numbers.add(1);
+        numbers.add(8);
+        numbers.add(3);
+        numbers.add(7);
+
+        System.out.println("List before: " + numbers);
+        System.out.println("Second smallest: " + secondSmallest(numbers));
+        System.out.println("List after: " + numbers);   
+    }
+
+    public static int secondSmallest(ArrayList<Integer> numbers) {
+        Collections.sort(numbers);
+        return (numbers.get(1));
+    }
+}
+
+Program outputs:
+List before: [5, 1, 8, 3, 7]
+Second smallest: 3
+List after: [1, 3, 5, 7, 8]
+
+
+
+
+CHANGE = SIDE EFFECT
+
+
+
+
+