YouTipJava9 Multirelease Jar
# Java 9 Multi-Release JAR
[!(#) Java 9 New Features](#)
The multi-release JAR feature allows you to create libraries that select which class version to use based on the specific Java runtime environment.
You specify the compilation version using the `--release` parameter.
The specific change is the addition of a new attribute in the `MANIFEST.MF` file under the `META-INF` directory:
Multi-Release: true
Additionally, a new `versions` directory is added under `META-INF`. If you want to support Java 9, there will be a `9` directory under the `versions` directory.
multirelease.jar
├── META-INF
│ └── versions
│ └── 9
│ └── multirelease
│ └── Helper.class
├── multirelease
│ ├── Helper.class
│ └── Main.class
In the following example, we use the multi-release JAR feature to generate two versions of a JAR file from `Tester.java`: one for JDK 7 and another for JDK 9. We then execute them in different environments.
**Step 1**
Create the folder `c:/test/java7/com/` and create a `Test.java` file in it with the following code:
## Example
```java
package com.;
public class Tester {
public static void main(String[] args){
System.out.println("Inside java 7");
}
}
**Step 2**
Create the folder `c:/test/java9/com/` and create a `Test.java` file in it with the following code:
## Example
```java
package com.;
public class Tester {
public static void main(String[] args){
System.out.println("Inside java 9");
}
}
Compile the source code:
```bash
C:test > javac --release 9 java9/com//Tester.java
C:JAVA > javac --release 7 java7/com//Tester.java
Create the multi-release JAR:
```bash
C:JAVA > jar -c -f test.jar -C java7 . --release 9 -C java9 .
Warning: entry META-INF/versions/9/com//Tester.java, multiple resources with same name
Execute using JDK 7:
```bash
C:JAVA > java -cp test.jar com..Tester
Inside Java 7
Execute using JDK 9:
```bash
C:JAVA > java -cp test.jar com..Tester
Inside Java 9
[!(#) Java 9 New Features](#)