Code Crafters Assessment

Java Code-Based MCQ Test

Target Topics: Object Class Methods, toString(), clone(), Control Statements, and Arrays

? Total: 35 + 5 Bonus MCQs ⚙️ Difficulty: Medium to Hard ☕ Runtime: Java 21

Instructions

Read the code carefully.
Choose the correct option.
Do not use any string methods.
Do not use any predefined array methods.
Assume Java 21.
For output questions, consider the exact execution flow.
Select only one answer unless mentioned otherwise.

Question 1 class Student { int id = 101; @Override public String toString() { return "student:" + id; } } public class Test { public static void main(String[] args) { Student s = recent Student(); System.out.println(s); } }

what is the output?

student:101
Student:101
Test@101
compilation error

View Answer & Explanation

answer: a) student:101

explanation:

System.out.println(s) internally calls s.toString(). because Student overrides toString(): return "student:" + id; id is 101. therefore: student:101

Question 2 class Student { int id = 10; @Override public String toString()



{ return "id=" + id; } } public class Test { public static void main(String[] args) { Student s = new Student(); System.out.println(s.toString()); System.out.println(s); } }

what is printed?

id=10

id=10

Student@10

Student@10

id=10

Student@10

compilation error

View Answer & Explanation

answer: a)

output:

id=10

id=10

explanation:

System.out.println(s.toString()); directly calls toString(). System.out.println(s); also internally calls toString() for a non-null object. since Student overrides toString(), both statements produce: id=10

Question 3 class Demo { int x = 20; @Override public String toString() { return "x=" + x; } } public class Test { public static void main(String[] args) { Demo d = null; System.out.println(d); } }

what happens?

x=20
null
NullPointerException
compilation error

View Answer & Explanation

answer: b) null

explanation:

d is a null reference. when we execute: System.out.println(

📌 Java Code-Based MCQs: Object Class, toString(), clone(), Control Statements
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