JDK v/s JRE

 

📌 To summarize:

Purpose	You Need	Tools Included
Just run Java code	JRE	JVM, Libraries
Write + run code	JDK	JRE + Compiler + Tools

✅ 1. Can you run Java code with only JRE?

Yes, if you already have compiled .class or .jar files.

📦 Example:
If someone gives you Hello.class or Hello.jar, and you have JRE, you can run it like this:

bash
java Hello        # runs Hello.class
java -jar Hello.jar  # runs Hello.jar

✅ JRE includes java (to run programs)

❌ JRE does NOT include javac, which is used to compile .java files

---

❌ 2. Can you compile Java code or create JAR files with only JRE?

No, because JRE does not have the compiler or packaging tools.

You cannot do:

bash
javac Hello.java       # ❌ Not available in JRE
jar cf Hello.jar *.class  # ❌ Not available in JRE

Those tools come only with JDK.

---

📦 Summary

Action	JRE ✅ / ❌	JDK ✅ / ❌
Run .class file (java)	✅	✅
Run .jar file	✅	✅
Compile .java file	❌	✅
Create .jar file	❌	✅

---

🔧 What You Need:

Use Case	You Need
Just run an existing .jar or .class app	✅ JRE is enough
Write Java code, compile, and package as JAR	✅ JDK is required

---

✅ Conclusion:

🔹 You need JDK if you're developing Java apps
🔹 You only need JRE if you're just running precompiled Java apps (like Minecraft, Jenkins, etc.)