`List ` and `List ` are the same class at runtime. Hence no `new T[]` and no `instanceof List `.

PECS: Producer-Extends, Consumer-Super. A `List ` produces Numbers; `List ` consumes Integers.

Question 1

What is Autoboxing in ServiceNow?

Accepted Answer

`int → Integer` (boxing), `Integer → int` (unboxing). Beware NullPointerException on unboxing a null Integer.

Question 2

What is equals / hashCode contract in ServiceNow?

Accepted Answer

Break this and HashMap/HashSet quietly misbehave. Always override both together; use IDE / records.

Question 3

What is Record in ServiceNow?

Accepted Answer

`record Point(int x, int y) {}` generates constructor, accessors, equals, hashCode, toString. Cannot extend other classes.

Question 4

What is Sealed class in ServiceNow?

Accepted Answer

`sealed interface Shape permits Circle, Square` enables exhaustive `switch` and a closed hierarchy.

Question 5

What is String pool in ServiceNow?

Accepted Answer

String literals are interned; `new String("a")` is not. `==` on literals can return true; use `.equals()`.

Question 6

What is var (local type inference) in ServiceNow?

Accepted Answer

`var list = new ArrayList<String>();` infers at compile time. Local only — not for fields, params, or returns.

Question 7

What is Generics erasure in ServiceNow?

Accepted Answer

`List` and `List` are the same class at runtime. Hence no `new T[]` and no `instanceof List`.

Question 8

What is Bounded wildcard in ServiceNow?

Accepted Answer

PECS: Producer-Extends, Consumer-Super. A `List` produces Numbers; `List` consumes Integers.

Question 9

What is try-with-resources in ServiceNow?

Accepted Answer

`try (var f = new FileReader(p)) { ... }` closes in reverse order even on exception. Suppressed exceptions kept on the primary.

Question 10

What is Pattern matching for instanceof in ServiceNow?

Accepted Answer

`if (o instanceof String s) { use(s); }` — no cast needed.

Question 11

What is Text Block in ServiceNow?

Accepted Answer

Triple-quoted `"""..."""`. Common indentation stripped automatically.

Question 12

What is Switch expression in ServiceNow?

Accepted Answer

`var s = switch(day) { case MON, TUE -> 1; default -> 0; };`. Combined with sealed types for exhaustiveness.

Question 13

What is Checked vs Unchecked in ServiceNow?

Accepted Answer

Checked extends Exception; must be declared or caught. Unchecked extends RuntimeException; not required.

Question 14

What is Optional in ServiceNow?

Accepted Answer

Use as return type to signal absence. Don't use for fields or method parameters — that's an antipattern.

Question 15

What is Stream API in ServiceNow?

Accepted Answer

`.filter().map().collect()`. Terminal operations trigger evaluation; intermediate are lazy. Single-use.

☕ CORE JAVA

Term Glossary