xSKILLby Infirals
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Java for Beginners

Java24 lessons4 hr 29 min

Learn Java from a first compile and run through variables, decisions, loops, collections, methods, and small classes.

Modules

Lessons open in reading order. Each one is a public page.

Starting out

3 lessons

Install a JDK, compile and run a first program, and store values in variables and primitive types.

  1. How Java runs and how to get set up10 min
  2. Your first program, line by line10 min
  3. Variables and primitive types11 min

Control flow and methods

4 lessons

Branch and repeat with conditions and loops, hold sequences in arrays and lists, then move shared work into methods.

  1. Operators and conditionals11 min
  2. Loops11 min
  3. Arrays and ArrayList12 min
  4. Methods12 min

Objects and text

5 lessons

Create objects with methods and constructors, then read, compare, build, and format strings.

  1. Classes and objects12 min
  2. Constructors and strings12 min
  3. String methods you will use daily11 min
  4. StringBuilder and readable formatting11 min
  5. Comparing strings: equals, ==, and ordering10 min

Inheritance, interfaces and polymorphism

6 lessons

Extend a class, override its behavior, organize code into packages, and share contracts through abstract classes and interfaces.

  1. Inheritance: building on a class11 min
  2. Overriding methods and using super11 min
  3. Packages, imports, and project layout10 min
  4. Abstract classes11 min
  5. Interfaces and multiple behaviors11 min
  6. Polymorphism, casting, and access control12 min

Exceptions, collections and modern Java

6 lessons

Handle failures and read input safely, then use lists, sets, maps, generics, enums, lambdas, streams, and files.

  1. Exceptions: try, catch, finally11 min
  2. Checked, unchecked, and throwing11 min
  3. Reading input with Scanner11 min
  4. Lists, sets, and maps12 min
  5. Generics and enums12 min
  6. Lambdas, streams, and files13 min
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