Java Certification Study Tool

✓ Solved: 0 ✗ Given up: 0 Total: 42

1

Java Basics

8 challenges

String Immutability Trap BEGINNER Strings → Operator Precedence Puzzle BEGINNER Operators → var Type Inference Trap BEGINNER Local Variable Type Inference → Text Block Surprise BEGINNER Text Blocks → Uninitialized Variable Mystery BEGINNER Variable Initialization → Underscore in the Wrong Place INTERMEDIATE Numeric Literals → The Constructor That Never Runs INTERMEDIATE Constructors → Initialization Order Puzzle INTERMEDIATE Instance Initializers →

2

Operators

6 challenges

The Stuck Post-Increment BEGINNER Increment and Decrement → The Unperformed Side Effect INTERMEDIATE Conditional vs Logical Operators → The Sneaky Single Equals BEGINNER Equality Operators → Two Shorts Don't Make a Short INTERMEDIATE Numeric Promotion → When Compound Operators Save the Day INTERMEDIATE Compound Assignment → The Ternary That Couldn't BEGINNER Ternary Operator →

3

Control Flow

6 challenges

The Dangling Else BEGINNER if / else → The Forgotten break BEGINNER switch Statement → The Block That Wouldn't yield INTERMEDIATE switch Expression → The Pattern Variable That Escaped INTERMEDIATE Pattern Matching → The Missing Weekend INTERMEDIATE switch Expression → The Break That Didn't INTERMEDIATE break / continue Labels →

4

Core APIs

8 challenges

Adding Apples and Strings BEGINNER String concatenation → The Off-By-One Substring BEGINNER String.substring → Two StringBuilders, One Truth INTERMEDIATE StringBuilder.equals → The Trimmed Twin INTERMEDIATE String pool & == → Are These Arrays Equal? BEGINNER Arrays.equals → Binary Search Sorted Backwards INTERMEDIATE Arrays.binarySearch → Two Variables, One Array Type BEGINNER Array declarations → The Date That Never Moves BEGINNER java.time immutability →

5

Methods

5 challenges

Varargs Ambiguity in Overloading ADVANCED Overloading → Static Method Hiding Trap ADVANCED Static Methods → The Unwanted Widener ADVANCED Overloading → The Shrinking Signature ADVANCED Overriding → The Exception Upgrade ADVANCED Overriding →

6

Class Design

4 challenges

Constructor Chaining and Checked Exceptions ADVANCED Inheritance → Variable Hiding in Polymorphism ADVANCED Polymorphism → The Ghost Gear ADVANCED Polymorphism → The Queue Jumper ADVANCED Constructors →

7

Beyond Classes

5 challenges

Static Interface Method Hiding ADVANCED Interfaces → Sealed Class Hierarchy Rules ADVANCED Sealed Classes → Record Compact Constructor Nuances ADVANCED Records → The Duplicate Default ADVANCED Interfaces → The Operation Gap ADVANCED Enums →