Collections: Lists, Maps, and Utilities

Use ArrayList and HashMap to manage dynamic data. Add, remove, search, and iterate over collections effectively.

Java Program Using HashMap

Program (Java)
Example & Expected Output

Stores key-value pairs and accesses them.

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Program Output 

                                    

                                

                            

                        

                                                

                            

                                
Java Program to Reverse a String

                                

                                    

                                        

                                            Program (Java)
                                            

                                                
                                                
                                            

                                        

                                        
                                        

                                    

                                    

                                        

                                            Example & Expected Output
                                            
                                        

                                        
Reverses a string using StringBuilder.

                                        
avaJ

                                        

                                            Program Output
                                            
                                        

                                        

                                    

                                

                            

                        

                                            
                    

                        

                            
Frequently Asked Questions

                            

                                

                                    

                                        
                                    

                                    

                                        

                                            Install a JDK (Java Development Kit), then compile with javac Main.java and run with java Main. On macOS, Linux, or Windows, use the official OpenJDK builds or your package manager.
                                        

                                    

                                

                                

                                    

                                        
                                    

                                    

                                        

                                            The examples target modern Java (Java 8 and above). If you use older versions, most examples will still work, but features like lambdas and streams require Java 8+.
                                        

                                    

                                

                                

                                    

                                        
                                    

                                    

                                        

                                            Yes. These examples are intended for learning. Copy the code, experiment with changes (e.g., different inputs), and observe the output to deepen your understanding of Java fundamentals.
                                        

                                    

                                

                                

                                    

                                        
                                    

                                    

                                        

                                            Yes. Java is platform-independent. The examples compile and run on major platforms (Windows, macOS, Linux) with a standard JDK.
                                        

                                    

                                

                            

                        

                    


                    

                        

                            
Learn Java the Practical Way

                            
Java powers enterprise applications, Android development, and countless backend systems. Practicing small, focused programs builds fluency with syntax and core concepts such as data types, control flow, methods, classes, interfaces, exceptions, collections, and streams.

                            
On this page, you will find clean, well-formatted examples that run across platforms. Each example includes a short description and expected output so you can quickly verify your understanding. Explore the topics via the sidebar and extend the code to experiment further.

                            
Whether you are preparing for interviews, working through coursework, or refreshing fundamentals, these examples offer a practical path to mastering Java. Bookmark the page and return often to keep improving.