Creating packages in Java - Visual Walkthrough

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Concept Flow - Creating packages

Write Java class with package declaration

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Save file in folder matching package name

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Compile Java file

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Run Java program using package path

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Program executes with package structure

This flow shows how to create a package by declaring it in code, saving files in matching folders, compiling, and running.

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Execution Sample

Java

package myapp.utils;

public class Helper {
    public static void greet() {
        System.out.println("Hello from Helper!");
    }
}

Defines a class Helper inside the package myapp.utils with a greet method that prints a message.

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Execution Table

Step	Action	File Location	Compilation Result	Runtime Output
1	Write Helper.java with package myapp.utils	myapp/utils/Helper.java	Not compiled yet
2	Compile Helper.java	myapp/utils/Helper.java	Compiled successfully
3	Write Main.java using Helper.greet()	myapp/Main.java	Not compiled yet
4	Compile Main.java	myapp/Main.java	Compiled successfully
5	Run Main with package path	Run command: java myapp.Main		Hello from Helper!
6	Program ends

💡 Program ends after printing the greeting message from Helper class.

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Variable Tracker

Variable	Start	After Step 2	After Step 4	After Step 5
Helper.class	Not exist	Exists in myapp/utils/	Exists	Used at runtime
Main.class	Not exist	Not exist	Exists in myapp/	Used at runtime

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Key Moments - 3 Insights

▶Why must the Helper.java file be saved inside the myapp/utils folder?

▶What happens if you try to run the Main class without compiling Helper first?

▶Why do we use the full package name when running the Main class?

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Visual Quiz - 3 Questions

Look at the execution_table at step 2, what is the compilation result for Helper.java?

A Compiled successfully

B Compilation error

C Not compiled yet

D Runtime error

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Concept Snapshot

Creating packages in Java:
- Use 'package package.name;' at the top of your .java file.
- Save the file inside folders matching the package name.
- Compile with javac from the root folder.
- Run using full package path (e.g., java package.MainClass).
- Packages organize code and avoid name conflicts.

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Full Transcript

This visual execution shows how to create and use packages in Java. First, you write a Java class with a package declaration, for example 'package myapp.utils;'. Then you save the file in a folder structure matching the package name, here 'myapp/utils/'. Next, you compile the Java file using javac. After compiling, you write another class that uses the first class, compile it, and then run the program using the full package path. The program prints the message from the Helper class. Key points include matching folder structure to package name, compiling before running, and using full package names to run classes.