nowshad-hasan

import io.github.solidpotato.PotatoMaker;
import org.springframework.boot.SpringApplication;

@org.springframework.boot.autoconfigure.SpringBootApplication
public class SpringBootApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootApplication.class, args);
        PotatoMaker.makePotato();
    }
}

nowshad-hasan

plugins {
    id 'java'
    id 'maven-publish'
    id 'signing'
}

sourceSets {
    main {
        java {
            srcDirs = ['src']

nowshad-hasan

plugins {
    id 'java'
}

group 'io.github.nowshad-hasan' // your group id
version '1.0-SNAPSHOT'

repositories {
    mavenCentral()
}

nowshad-hasan

void checkLocalInterface() {
        interface Runner {
            void run();
        }

        Runner runner = () -> System.out.println("Running");
        runner.run();
    }

void checkLocalEnum() {

nowshad-hasan

public class FileMismatchExample {

    /*
    Here, hello1 and hello3 have same content, hello2 has different content.
     */
    public static void main(String[] args) {
        Path path1 = Path.of("hello1.txt");
        Path path2 = Path.of("hello2.txt");
        Path path3 = Path.of("hello3.txt");

nowshad-hasan

    String input = "Hello Java 17!\nIt's a new LTS.";

    public static void indentString(String input) {
        // Positive value add spaces beginning of each line.
        String positiveIndent5 = input.indent(5); // 5 spaces
      /*
       1.     Hello Java 17!
              It's a new LTS.
      */

nowshad-hasan

public class NullPointerExceptionExample {

    /*
    Stack trace at Java 1.8: Exception in thread "main" java.lang.NullPointerException
	at exception.NullPointerException.main(NullPointerException.java:14)

    Stack trace at Java 17: Exception in thread "main" java.lang.NullPointerException:
    Cannot read field "birthPlace" because "book.author" is null at
    others.NullPointerExceptionExample.main(NullPointerExceptionExample.java:14)
     */

nowshad-hasan

public class SealedClassWithRecordExample {
    sealed interface Exam permits Student {
        void giveExam();
    }

    record Student(String name, String rollNumber) implements Exam {
        @Override
        public void giveExam() {

        }

nowshad-hasan

/*
    Interface can be sealed or non-sealed, and it can permit other interface or class.
    Permitted interface must be sealed/non-sealed and class must be sealed/non-sealed/final.
    Sealed interface and permitted interface/class must be in same module. For unnamed module, they must be in same package.
 */
public sealed interface Move permits Fly, Run {
    void move();
}

// Fly is non-sealed. So, it can be implemented by any class or extended by any interface.

nowshad-hasan

// Which classes are permitted to extend this Liquid class, must be sealed/non-sealed/final.
public sealed class Liquid permits Water, Honey, Milk {}

// Now, Water can be extended by any class
public non-sealed class Water extends Liquid {}

// Honey is final. So, it can't be extended by anyone.
public final class Honey extends Liquid {}

// Milk is sealed. So, it starts another sealed hierarchy.