Introduction to Programming

Comparing with another collection

Every Java collection implements the equals() method, which compares it with another collection. In the case of List, two lists are considered equal (the method list1.equals(list2) returns true) when:

• Each collection is of type List
• Each element of one list is equal to the element of another list in the same position

Here is the code that illustrates it:

List<String> list1 = new ArrayList<>();list1.add("s1");list1.add("s2");List<String> list2 = new ArrayList<>();list2.add("s1");list2.add("s2");System.out.println(list1.equals(list2)); //prints: truelist2.sort(Comparator.reverseOrder());System.out.println(list2);               //prints: [s2, s1]System.out.println(list1.equals(list2)); //prints: false

If two lists are equal, ...