This chapter is about Java 15 – Pattern matching in instanceof.
Java 14 introduces instanceof operator to have type test pattern as is a preview feature. Type test pattern has a predicate to specify a type with a single binding variable. It continues to be a preview feature in Java 15 as well.
Syntax
if (person instanceof Employee e) {
return e.getEmployeeId();
}
Example
Consider the following example −
ApiTester.java
public class APITester {
public static void main(String[] args) {
Person manager = new Manager(23, "Robert");
manager.name = "Robert";
System.out.println(getId(manager));
}
public static int getId(Person person) {
if (person instanceof Employee e) {
return e.getEmployeeId();
}
else if (person instanceof Manager m) {
return m.getManagerId();
}
return -1;
}
}
abstract sealed class Person permits Employee, Manager {
String name;
String getName() {
return name;
}
}
final class Employee extends Person {
String name;
int id;
Employee(int id, String name){
this.id = id;
this.name = name;
}
int getEmployeeId() {
return id;
}
}
non-sealed class Manager extends Person {
int id;
Manager(int id, String name){
this.id = id;
this.name = name;
}
int getManagerId() {
return id;
}
}
Compile and Run the program
$javac -Xlint:preview --enable-preview -source 14 APITester.java $java --enable-preview APITester
Output
23
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