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Core automation track

Java for Automation

The 20% of Java that powers 100% of your framework code.

What this track covers

OOP in framework designCollections & HashMapGenericsException handlingJava 8 StreamsLambda & OptionalString manipulationInterfaces vs abstract classes

Collections in a framework

Collections model test data, locator maps and report rows. Choosing the wrong one costs determinism or performance.

Why it is required: Interviewers use Collections to check whether you write framework code or just scripts.

Example: Reading login rows from JSON into a List<Map<String, String>> for a DataProvider.

java
1public static Object[][] rows(String path) {
2    List<Map<String, String>> data = JsonReader.readList(path);
3    return data.stream()
4            .map(row -> new Object[]{ row.get("user"), row.get("pass"), row.get("expected") })
5            .toArray(Object[][]::new);
6}

Expected result

A DataProvider-ready Object[][] built from an external JSON file, with no hardcoded data.

Common mistakes

  • Using HashMap where report ordering matters (use LinkedHashMap)
  • Raw types instead of generics
  • Loading the same file once per test instead of caching

Why LinkedHashMap over HashMap in a reporting utility?

Java 8 Streams in tests

Streams turn verbose data validation loops into readable declarative assertions.

Why it is required: Almost every SDET coding round includes at least one Stream question.

Example: Assert every returned order belongs to the requested customer.

java
1List<Order> orders = OrderApi.forCustomer(7);
2 
3assertTrue(orders.stream().allMatch(o -> o.customerId() == 7));
4 
5Map<String, Long> byStatus = orders.stream()
6        .collect(Collectors.groupingBy(Order::status, Collectors.counting()));

Expected result

A single readable assertion plus a status breakdown map for reporting.

Common mistakes

  • Reusing a consumed stream (IllegalStateException)
  • Side effects inside forEach instead of collecting
  • Using parallelStream() on tiny collections

Difference between map() and flatMap()?

Related interview questions

Open bank

  • Difference between HashMap, LinkedHashMap and TreeMap?

    HashMap = no order, O(1) average; LinkedHashMap = insertion (or access) order; TreeMap = sorted by key, O(log n), backed by a red-black tree.

  • How do you find duplicate characters in a String using Java 8 Streams?

    Stream the chars, group by identity with counting, filter entries with count > 1.

  • Abstract class vs interface — which do you use in your framework and why?

    Abstract class for shared state + partial implementation (BasePage, BaseTest); interface for capability contracts (Reportable, DataProvider strategy).

  • How do you choose between ArrayList, LinkedList, HashMap and HashSet in test code?

    ArrayList for ordered, index-accessed data, HashMap for key lookups such as test data by id, HashSet for uniqueness checks, LinkedList almost never in test frameworks.

  • How does HashMap work internally, and why must hashCode and equals agree?

    HashMap stores entries in buckets chosen by hashCode; equals resolves collisions inside a bucket. If two equal objects return different hash codes they land in different buckets and lookups silently fail.

  • Interface vs abstract class — how does that decision show up in a test framework?

    Abstract classes share state and common behaviour (BasePage, BaseTest); interfaces declare capability contracts (Reportable, DriverProvider) and allow multiple inheritance of type.

Quick reference available

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