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// File: JvmDemo.java
// Demonstrates compilation units, packages, and basic JVM information

package com.example.intro;  // maps to directory: com/example/intro/

public class JvmDemo {

public static void main(String[] args) {

// ---- Runtime / JVM info ----
        Runtime rt = Runtime.getRuntime();

long maxMemory  = rt.maxMemory()  / (1024 * 1024); // convert to MB
        long totalMemory = rt.totalMemory() / (1024 * 1024);
        long freeMemory  = rt.freeMemory()  / (1024 * 1024);
        int  processors  = rt.availableProcessors();

System.out.println("=== JVM Runtime Information ===");
        System.out.printf("Max heap memory  : %d MB%n", maxMemory);
        System.out.printf("Total heap memory: %d MB%n", totalMemory);
        System.out.printf("Free heap memory : %d MB%n", freeMemory);
        System.out.printf("Available CPUs   : %d%n",   processors);

// ---- System properties ----
        System.out.println("
=== Key System Properties ===");
        String[] keys = {"java.version", "java.vendor", "os.name", "user.dir"};
        for (String key : keys) {
            System.out.printf("%-20s = %s%n", key, System.getProperty(key));
        }
    }
}