Installing JDK

Java Requirements for HGrid247-3.5

Explanation

HGrid247 requires the Java Development Kit (JDK) because:

The workflow will be compiled into Java code.
The result is a MapReduce/Spark/Flink/Beam application (.jar)
This process requires a compiler (javac)

JRE alone is not enough , because:

JRE is only for running programs
Doesn't have a compiler

Required JDK Version

HGrid247-3.5 is compiled using:
```
    JDK 1.8 (Java 8)
    
```
So requirement:
```
    JDK ≥ 1.8
    
```

Important Recommendations

Use the same JDK version as the Hadoop cluster where the application is running.

Why?

Because of Apache Hadoop :

Very sensitive to Java version differences
Can cause:
- error runtime
- incompatibility class
- job failed to run

Example Scenario

    Environment                 JDK
    -----------------------------------
    Laptop (development)	JDK 1.8
    Cluster Hadoop              JDK 1.8
    HGrid247                    JDK 1.8

✅ Safe → compatible

Problematic Examples

    Environment                 JDK
    ----------------------------------
    Laptop (development)        JDK 17
    Cluster Hadoop              JDK 8

❌ Risks:

error when submitting job
incompatibility bytecode (class file major version)

How to Check Java Version

In the terminal:

    java -version
    javac -version

Recommended Setup

For stability:

Use:
- JDK 1.8 (most secure)
- or the same JDK as the cluster
Set environment variable

🔢 Java Version → Class File Major Version

    Java Version	Major Version
    -----------------------------
    Java SE 23          67
    Java SE 22          66
    Java SE 21          65
    Java SE 20          64
    Java SE 19          63
    Java SE 18          62
    Java SE 17          61
    Java SE 16          60
    Java SE 15          59
    Java SE 14          58
    Java SE 13          57
    Java SE 12          56
    Java SE 11          55
    Java SE 10          54
    Java SE 9           53
    Java SE 8           52
    Java SE 7           51
    Java SE 6.0         50
    Java SE 5.0         49
    JDK 1.4             48
    JDK 1.3             47
    JDK 1.2             46
    JDK 1.1             45

📌 Important Notes

On HGrid247-3.5 built using JDK 1.8 , then:
Class file major version = 52
This means that the workflow you compile must use JDK 8 or later , but must not run on a JVM lower than 52 .

If an error appears like:

    Unsupported major.minor version XX

     class file version XX.0 does not support...

So the cause is that the JDK used is lower than what is required .

🎯 How to Check Class Version of File .class or.jar

Use:

    javap -verbose NamaClass.class | find "major"

Example:

    major version: 52

This means the file was created by Java 8 .