Java 25 Feature: Flexible Code Compilation by Pran Sukh

Java 25 Example: Primitive Pattern Matching

/* In java 25 you need explicit definition of class and main method, just for start it's easy to understand the execution.
 * But in real Object-Oriented applications you cannot go without classes and inheritance */

void main(){
    int i = 3;
    char any = 'P';

    oldWayOfUnBoxing(i);
    oldWayOfUnBoxing(any);

    checkObject(i);
    checkObject(any);
}

static void oldWayOfUnBoxing(Object obj) {
    if (obj instanceof Integer) {
        int i = ((Integer) obj).intValue(); // First obj is boxed to Integer then unboxed to int with .intValue of Integer class
        log("Primitive obj of type int is converted/unboxed to int with Integer class");
    }
    if (obj instanceof Character) {
        char c = ((Character) obj).charValue(); // First obj is boxed to Character then unboxed to char with .charValue of Character class
        log("Primitive obj of type char is converted/unboxed to char with Character class");
    }
}

/* Feature: primitive types in Java’s pattern-matching framework introduced in JEP 507 */
static void checkObject(Object o){
    if(o instanceof int i){ // if o is type int then bind it to i, no extra boilerplate code.
        log("primitive int is converted to int without any extra unboxing");
    }
    if(o instanceof char c){ // if o is type char then bind it to c
        log("primitive char is converted to char without any extra unboxing");
    }
}

static void log(String msg){
    System.out.println(msg);
}
    

If you face any issue to run this code, just for your information this feature in Java is still in preview — you need to enable this while compilation.

First copy the code and create a file with any name like PatternMatching.java

Place the file inside the jdk-25/bin/ folder.

Then run the following commands:

javac --enable-preview --release 25 PatternMatching.java

Then simply run the program with:

java --enable-preview PatternMatching

(pransukh.21@gmail.com)