Java Programming Cheat Sheet

1. Java Platform and Memory Model

Java's reputation rests on the famous "Write Once, Run Anywhere" principle, and that promise is delivered by a layered software stack. The Java Virtual Machine (JVM) is an abstract...

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2. Core Language Features

Java's type system rests on eight primitive data types that map directly to hardware: byte (8-bit), short (16-bit), int (32-bit), long (64-bit), float (32-bit IEEE 754), double (64...

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3. Object-Oriented Programming

Object-oriented design in Java rests on four pillars. Encapsulation bundles an object's data and methods together, restricting direct access by marking fields private and exposing...

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4. Generics and the Collections Framework

Generics let classes, interfaces, and methods operate on parameterized types, providing compile-time type safety and eliminating most casts. List<String> names = new ArrayLis...

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5. Functional Programming and the Streams API

The arrival of lambdas in Java 8 transformed the language from verbose anonymous classes into concise functional expressions. A lambda implements a functional interface—an interfac...

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6. Concurrency and the Java Memory Model

Java supports concurrent execution of multiple threads within a single program. Threads can be created by extending Thread and overriding run(), by implementing the Runnable interf...

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7. Exception Handling, I/O, and Serialization

Java's exception model centers on the Throwable hierarchy. Throwables split into Error (serious, unrecoverable conditions such as OutOfMemoryError and StackOverflowError, which app...

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8. Modern Java, Design Patterns, and Best Practices

Java 9 introduced the Java Platform Module System (JPMS, Project Jigsaw), which groups packages into modules declared in a module-info.java file. The key clauses are requires (depe...

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