intermediate · No code
Java Refresher
Refresh Java's object-oriented structure, interfaces, collections, exceptions, and generics. Build confidence reading and modifying everyday Java code through focused syntax and API review.
What you'll be able to do
- Trace how Java class definitions, constructors, object creation, references, fields, and methods work together.
- Explain how List, Set, and Map implementations differ in ordering, uniqueness, indexing, keys, values, and replacement behavior.
- Predict collection contents, retrieved values, sizes, and observable iteration behavior after a sequence of Java operations.
- Analyze unfamiliar Java snippets by connecting object references and member access to the resulting program state.
Who this is for
This course is for learners who have seen basic Java before and want a focused refresher on reading and modifying everyday object-oriented Java code. It fits anyone who needs to regain fluency with classes, objects, and the core List, Set, and Map collection types.
What you should already know
- Some prior exposure to Java syntax, including variables, methods, and basic expressions.
- The ability to read simple Java code and understand primitive values, assignment, and method calls.
How a lesson actually goes
Person p = new Person();: which part defines the type, and which part creates the instance?Person is the type, and new Person() creates the instance. I think p is the object, though, because it is the variable I use to call methods.p is the reference variable, not the object itself; it refers to the instance created by new Person(). That is why assigning another reference can make two variables access the same object's fields and methods. Let us test that distinction with a small class and trace what changes after a method call.Written from this course's first lesson to show the format — not a recording of a real session.
Course content
marks each module's capstone lesson.
01Object-Oriented Foundations4 lessons
Establish the core Java model of classes and objects, including how class definitions describe structure and how object instances hold state and support behavior.
Course Introduction
Welcome and orientation: review Java's object-oriented structure, interfaces, collections, exceptions, and generics, and learn how the modules build confidence reading and modifying everyday Java code.
Classes
A class is a blueprint for a Java type. Learn to identify the members that define an object's state and behavior and recognize how constructors initialize instances.
Objects
Objects are runtime instances of classes. Learn how the new expression creates an instance, how variables hold object references, and how member access invokes the instance's behavior.
Object-Oriented Foundations Assessment
Synthesize the class and object model by tracing how a class becomes a runtime instance, how its state is initialized, and how references invoke its defined behavior.
02Collection Reasoning4 lessons
Interpret Java's core collection abstractions and reason about how lists, sets, and maps store, retrieve, and organize values. Apply API knowledge to trace collection-focused code and predict its behavior.
List
A List represents an ordered sequence of elements. Learners examine common operations such as adding, retrieving, replacing, and removing values while reasoning about how indexes and duplicates affect behavior.
Set
A Set models a collection of distinct elements rather than a sequence addressed by index. Learners reason about duplicate insertion, membership checks, removal, and the implications of set iteration order.
Map
A Map stores associations between keys and values, with each key identifying at most one current value. Learners trace operations such as put, get, containsKey, and remove, including what happens when an existing key is reused.
Collection Code Reasoning
This synthesis assessment requires reasoning across Java's core collection abstractions. Learners analyze sequential mutations, duplicate handling, key replacement, lookups, and iteration to predict final state and output.
Questions
Is this course suitable if I have never programmed in Java?
It is designed as a refresher rather than a first programming course. You should already be able to read simple Java statements and recognize variables and methods; the course then rebuilds your understanding of classes, objects, and collections.
Will I practice with real Java code or only memorize definitions?
The lessons focus on tracing and analyzing code. You will reason about constructors, references, member access, collection operations, retrieved values, sizes, and iteration behavior.
What collection types are covered?
The collection sequence covers List, Set, and Map, including ordering, indexed access, duplicates, uniqueness, keys, values, lookup, replacement, removal, and combined collection reasoning.
Does the course teach Java from the beginning?
No. It reviews foundational object-oriented Java concepts and core collection behavior, but it does not serve as a complete introduction to programming or Java syntax.
Will I learn the differences between classes and objects?
Yes. You will examine how a class defines a type and how Java creates object instances that references can use to access state and behavior.
The first lesson is ten minutes away.
Free while codeset is early. You choose what you're building before the first lesson starts, and the course is taught around it.