Java SE 21 Developer ProfessionalPractice Test

Create program flow control constructs including if/else, switch statements and expressions, loops, and break and continue statements

• Declare and instantiate Java objects including nested class objects, and explain the object life-cycle
• Create classes and records, and define and use instance and static fields and methods, constructors, and instance and static initializers

• Implement overloaded methods, including var-arg methods
• Understand variable scopes, apply encapsulation, and create immutable objects. Use local variable type inference

• Implement inheritance, including abstract and sealed types as well as record classes
• Override methods, including that of the Object class
• Implement polymorphism and differentiate between object type and reference type
• Perform reference type casting, identify object types using the instanceof operator, and pattern matching with the instanceof operator and the switch construct

• Create and use interfaces, identify functional interfaces, and utilize private, static, and default interface methods
• Create and use enum types with fields, methods, and constructors

Handle exceptions using try/catch/finally, try-with-resources, and multi-catch blocks, including custom exceptions

Create arrays, List, Set, Map and Deque collections, and add, remove, update, retrieve and sort their elements

• Use Java object and primitive Streams, including lambda expressions implementing functional interfaces, to create, filter, transform, process, and sort data
• Perform decomposition, concatenation, and reduction, and grouping and partitioning on sequential and parallel streams

• Define modules and expose module content, including that by reflection, and declare module dependencies, define services, providers, and consumers
• Compile Java code, create modular and non-modular jars, runtime images, and implement migration to modules using unnamed and automatic modules

• Create both platform and virtual threads. Use both Runnable and Callable objects, manage the thread lifecycle, and use different Executor services and concurrent API to run tasks
• Develop thread-safe code, using locking mechanisms and concurrent API
• Process Java collections concurrently and utilize parallel streams

• Read and write console and file data using I/O streams
• Serialize and de-serialize Java objects
• Construct, traverse, create, read, and write Path objects and their properties using the java.nio.file API

• Implement localization using locales and resource bundles
• Parse and format messages, dates, times, and numbers, including currency and percentage values