Java 17 Features

import java.util.List;

public class RecordDemo {
    // One line replaces fields, constructor, getters,
    // equals(), hashCode() and toString()
    record Employee(String name, String dept, double salary) {

        // Compact constructor: validate without repeating the fields
        Employee {
            if (salary < 0) {
                throw new IllegalArgumentException("salary < 0");
            }
        }

        // Records can have methods and static factories
        double yearly() {
            return salary * 12;
        }

        static Employee intern(String name) {
            return new Employee(name, "Training", 15000);
        }
    }

    public static void main(String[] args) {
        Employee asha = new Employee("Asha", "IT", 85000);
        Employee same = new Employee("Asha", "IT", 85000);

        System.out.println(asha);
        System.out.println("name()   = " + asha.name());
        System.out.println("yearly() = " + asha.yearly());
        System.out.println("equals   = " + asha.equals(same));
        System.out.println("intern   = " + Employee.intern("Ravi"));

        List<Employee> team = List.of(asha, Employee.intern("Meera"));
        team.forEach(e -> System.out.println(e.name() + " -> " + e.dept()));

        try {
            new Employee("Bad", "IT", -1);
        } catch (IllegalArgumentException e) {
            System.out.println("Rejected: " + e.getMessage());
        }
    }
}

Employee[name=Asha, dept=IT, salary=85000.0]
name()   = Asha
yearly() = 1020000.0
equals   = true
intern   = Employee[name=Ravi, dept=Training, salary=15000.0]
Asha -> IT
Meera -> Training
Rejected: salary < 0

public class InstanceofPatternDemo {
    static String describe(Object obj) {
        // Before Java 16: test, then cast
        //   if (obj instanceof String) {
        //       String s = (String) obj; ...
        //   }

        // Java 16+: test and bind a variable in one step
        if (obj instanceof String s) {
            return "String of length " + s.length();
        }
        // The variable can be used in the same condition
        if (obj instanceof Integer i && i > 100) {
            return "Large integer " + i;
        }
        if (obj instanceof Integer i) {
            return "Integer " + i;
        }
        if (!(obj instanceof int[] arr)) {
            return "Something else: " + obj;
        }
        // arr is in scope here because the test above returned
        return "int array with " + arr.length + " items";
    }

    public static void main(String[] args) {
        Object[] values = { "Java 17", 42, 500, new int[] { 1, 2, 3 }, 3.14 };
        for (Object v : values) {
            System.out.println(describe(v));
        }
    }
}

String of length 7
Integer 42
Large integer 500
int array with 3 items
Something else: 3.14

public class TextBlockDemo {
    public static void main(String[] args) {
        // Before: escapes and concatenation
        String oldJson = "{\n" +
                "  \"name\": \"Asha\",\n" +
                "  \"role\": \"Developer\"\n" +
                "}";

        // Java 15+: a text block keeps the layout as written
        String json = """
                {
                  "name": "Asha",
                  "role": "Developer"
                }""";
        System.out.println(json);
        System.out.println("Same text: " + json.equals(oldJson));

        // Combine with formatted() for templates
        String sql = """
                SELECT id, name
                FROM employee
                WHERE dept = '%s'
                """.formatted("IT");
        System.out.print(sql);

        // \ joins lines, \s keeps a trailing space
        String line = """
                Java 17 is a \
                long-term-support release.\s""";
        System.out.println("[" + line + "]");
    }
}

{
  "name": "Asha",
  "role": "Developer"
}
Same text: true
SELECT id, name
FROM employee
WHERE dept = 'IT'
[Java 17 is a long-term-support release. ]

import java.util.random.RandomGenerator;
import java.util.random.RandomGeneratorFactory;

public class RandomDemo {
    public static void main(String[] args) {
        // One interface for all random number generators
        RandomGenerator legacy = new java.util.Random(7);
        System.out.println("Random   : " + legacy.nextInt(100));

        // Pick an algorithm by name (seeded so output is repeatable)
        RandomGenerator lxm = RandomGeneratorFactory
                .of("L64X128MixRandom")
                .create(42);
        System.out.println("L64X128  : " + lxm.nextInt(1, 7));

        // New range methods on every generator
        System.out.println("dice     : " + lxm.ints(5, 1, 7)
                .boxed().toList());

        // Default algorithm without choosing one yourself
        RandomGenerator any = RandomGenerator.getDefault();
        int n = any.nextInt(10, 20);
        System.out.println("default  : " + (n >= 10 && n < 20));

        System.out.println("Some algorithms:");
        RandomGeneratorFactory.all()
                .map(RandomGeneratorFactory::name)
                .filter(name -> name.startsWith("L") || name.equals("Random"))
                .sorted()
                .limit(4)
                .forEach(name -> System.out.println("  " + name));
    }
}

Random   : 36
L64X128  : 1
dice     : [2, 1, 1, 4, 4]
default  : true
Some algorithms:
  L128X1024MixRandom
  L128X128MixRandom
  L128X256MixRandom
  L32X64MixRandom

# Garbage collectors: ZGC and Shenandoah are production-ready (Java 15)
java -XX:+UseZGC App
java -XX:+UseShenandoahGC App

# JDK internals are strongly encapsulated (JEP 403). Code that uses
# reflection on internal APIs now fails unless you open the package:
java --add-opens java.base/java.lang=ALL-UNNAMED -jar app.jar

# Inspect a running application with Flight Recorder streaming
jcmd <pid> JFR.start name=live

# Deprecated for removal: Security Manager, Applet API
# Removed: RMI Activation, experimental AOT and Graal JIT compilers
# New ports: macOS on Apple Silicon (AArch64)