Java Level 2 Test

Naveen AnamaneniUpdated Nov 14, 2026 · 8 min read

mediumJava 25java test quiz oop assessment

Before a driving test, most learners can steer, brake and park. What the examiner checks is whether they can do all of it together, in the right order, without someone beside them saying what comes next. Object-oriented Java is similar. You may know each idea on its own: constructors, inheritance, overriding, interfaces. This test checks whether you can tell which rule applies when they meet in the same few lines of code.

How the Test Works

What's in it: 20 multiple-choice questions, then 3 output puzzles where you work out what a short program prints.
Time: 30 minutes, without notes, an IDE or JShell.
Pass mark: 16 out of 23. The quiz marks the 20 questions for you. Mark the puzzles yourself, one point each, and add them to your quiz score.
What it covers: the lessons from "Classes and Objects" to "SOLID Principles in Java" and the design patterns.

Part 1: 20 Questions

Level 2 test: 20 questions

20 questions

1When new B() runs for the first time, which runs first?

B's constructorAn instance initializer blockmainA static block of the class

2A class declares only the constructor A(int x) {}. What does new A() do?

It calls a default constructorIt sets x to 0It throws an exception at runtimeIt causes a compile error

3In Java 25, what may appear before an explicit super(...) call in a constructor?

Nothing at allCalls to instance methodsStatements that don't use the object being built, such as argument checksA return statement

4Can a static method be overridden?

No; a subclass static method with the same signature hides itYesOnly in interfacesOnly if it is final

5When is the overloaded method to call chosen?

At runtimeWhen the class is loadedAt randomAt compile time

6Which access level allows the same package and subclasses in other packages?

protectedprivateDefault (no modifier)Only public

7An interface method with no body and no default, static or private modifier is implicitly:

protected abstractpublic abstractpublic finalPackage-private

8Fields declared in an interface are implicitly:

privatepublic static finalprotectedInstance fields

9What may an overriding method return?

Any typeThe same type, or a subtype of the original return typeOnly ObjectOnly a primitive

10What does Integer c = 128, d = 128; System.out.println(c == d); print?

trueA compile errorfalseA NullPointerException

11What does the default Object.equals() compare?

Field valuesHash codesThe toString() outputReferences (identity)

12If a.equals(b) is true, then:

The hash codes must differa.hashCode() == b.hashCode() must be trueNothing is requireda == b must be true

13Can an abstract class have a constructor?

Yes, and subclasses call it with super(...)NoOnly a private oneOnly if it has no abstract methods

14Which nested class does not need an instance of the outer class?

Member inner classLocal classStatic nested classAnonymous class

15Which is true of a record?

Its fields are private final, and the record class is implicitly finalIt can extend another classIt has settersIts fields are public and can be changed

16Each permitted subclass of a sealed class must be declared:

abstractfinal, sealed or non-sealedstaticpublic

17"Open for extension, closed for modification" is which SOLID principle?

Single responsibilityLiskov substitutionOpen/closedDependency inversion

18Which pattern builds a complex object step by step?

BuilderSingletonObserverStrategy

19What does Animal a = new Dog(); Cat c = (Cat) a; cause?

A compile errorc becomes nullA ClassCastException at runtimeNothing

20Enum constructors are implicitly:

publicprotectedstaticprivate

Show answers

A static block of the class: Static blocks run once, when the class is first initialized, before any object of it exists. Revise: Static Block.
It causes a compile error: The compiler adds a no-argument constructor only when a class declares no constructors at all. Revise: Constructors in Java.
Statements that don't use the object being built, such as argument checks: Flexible constructor bodies allow code before super(...) as long as it doesn't touch this. Revise: Flexible Constructor Bodies.
No; a subclass static method with the same signature hides it: Static methods are chosen at compile time from the declared type, so they are hidden, not overridden. Revise: Can Static, Private and Final Methods Be Overridden.
At compile time: The compiler picks an overload from the argument types it can see. Revise: Compile-Time Polymorphism in Java.
protected: protected means the same package plus subclasses anywhere. Revise: Access Modifiers in Java.
public abstract: Abstract interface methods are always public abstract, whether you write the words or not. Revise: Interfaces in Java.
public static final: Interface fields are constants shared by every implementing class. Revise: Interfaces in Java.
The same type, or a subtype of the original return type: This is called a covariant return type. Revise: Covariant Return Type in Java.
false: By default only -128 to 127 are cached, so 128 is boxed into two different objects, and == compares references. Revise: Integer Cache in Java.
References (identity): Object.equals is simply this == obj. Revise: Object Class in Java.
a.hashCode() == b.hashCode() must be true: Equal objects must have equal hash codes, or hash-based collections break. Revise: Object Equality and Hash Codes in Java.
Yes, and subclasses call it with super(...): The constructor sets up the abstract class's own fields when a subclass object is built. Revise: Abstract Classes and Abstract Methods.
Static nested class: A static nested class has no hidden reference to an outer object. Revise: Static Nested Class in Java.
Its fields are private final, and the record class is implicitly final: Records are shallowly immutable, final data carriers. Revise: Records in Java.
final, sealed or non-sealed: Every subclass has to say whether the hierarchy stops, stays closed or opens up again. Revise: Sealed Classes and Interfaces in Java.
Open/closed: The open/closed principle: add new behavior with new code, not by editing working code. Revise: SOLID Principles in Java.
Builder: A builder sets one part at a time and creates the object at the end. Revise: Builder Pattern in Java.
A ClassCastException at runtime: The cast compiles, because an Animal might be a Cat, but this object is a Dog. Revise: Upcasting and Downcasting.
private: Only the enum itself can create its constants. Revise: Enums in Java.

Part 2: Output Puzzles

Work out what each program prints, on paper, before you open the solution. The solution shows the full program, its real output and a Try it button. Give yourself one point for each puzzle you get exactly right.

Puzzle 1: Who Prints First

What does new B(); new B(); print?

Java

class A {
    static { System.out.print("1"); }
    { System.out.print("2"); }
    A() { System.out.print("3"); }
}
 
class B extends A {
    static { System.out.print("4"); }
    { System.out.print("5"); }
    B() { System.out.print("6"); }
}

Show solution

InitOrderPuzzle.java▶ Try it

class A {
    static { System.out.print("1"); }
    { System.out.print("2"); }
    A() { System.out.print("3"); }
}
 
class B extends A {
    static { System.out.print("4"); }
    { System.out.print("5"); }
    B() { System.out.print("6"); }
}
 
public class InitOrderPuzzle {
    public static void main(String[] args) {
        new B();
        new B();
        System.out.println();
    }
}

Output

1423562356

Why this output?

The static blocks run once, parent first: 1, then 4. Then, for each object, the parent part is built before the child part: the parent's instance block and constructor (2, 3), then the child's instance block and constructor (5, 6). The second object repeats only 2356, because static blocks never run twice. Revise: Order of Initialization.

Puzzle 2: Same Name in Both Classes

What is printed?

Java

class Parent {
    String name = "Parent";
    String show() { return "Parent"; }
}
 
class Child extends Parent {
    String name = "Child";
    String show() { return "Child"; }
}
 
// in main:
Parent p = new Child();
System.out.println(p.name + " " + p.show());

Show solution

FieldPuzzle.java▶ Try it

class Parent {
    String name = "Parent";
    String show() { return "Parent"; }
}
 
class Child extends Parent {
    String name = "Child";
    String show() { return "Child"; }
}
 
public class FieldPuzzle {
    public static void main(String[] args) {
        Parent p = new Child();
        System.out.println(p.name + " " + p.show());
    }
}

Output

Parent Child

Why this output?

Fields are never overridden. p.name is chosen from the declared type, Parent. Methods are overridden, so p.show() runs the version of the real object, a Child. Revise: Runtime Polymorphism and Dynamic Method Dispatch.

Puzzle 3: Passing Null to an Overloaded Method

What is printed?

Java

static void m(Object o) { System.out.println("Object"); }
static void m(String s) { System.out.println("String"); }
 
public static void main(String[] args) {
    m(null);
}

Show solution

OverloadPuzzle.java▶ Try it

public class OverloadPuzzle {
    static void m(Object o) { System.out.println("Object"); }
    static void m(String s) { System.out.println("String"); }
 
    public static void main(String[] args) {
        m(null);
    }
}

Output

String

Why this output?

null fits both methods. When more than one overload fits, the compiler picks the most specific one, and String is more specific than Object. If there were also an m(Integer), the call would be ambiguous and wouldn't compile. Revise: Method Overloading in Java.

What Your Score Means

Score (out of 23)	What it means	What to do next
20 to 23	You think in objects	Move on to Strings in Java
16 to 19	A pass, with a few gaps	Read the lessons linked from the questions you missed, then move on
Under 16	Not yet	Reread the lessons behind your wrong answers, build a small class hierarchy of your own, and take the test again

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How the Test Works

Part 1: 20 Questions

Part 2: Output Puzzles

Puzzle 1: Who Prints First

Puzzle 2: Same Name in Both Classes

Puzzle 3: Passing Null to an Overloaded Method

What Your Score Means

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