Null Checked Singleton Object

To avoid eagerly creating of singleton object, The object creation needs to be on-demand. in the below code, the object creation will only happen when the getAppleInstance method will be called, but the getAppleInstance method can be called multiple times and it can be used to create multiple Singleton objects as shown below.

package org.wesome.dsalgo.design.pattern.singleton;

public class Apple {
    static Apple appleInstance;

    public Apple() {
        System.out.println("Apple default constructor");
    }

    public static Apple getAppleInstance() {
        System.out.println("Apple getAppleInstance");
        appleInstance = new Apple();
        return appleInstance;
    }
}

package org.wesome.dsalgo.design.pattern.singleton;

public class SingletonClass {
    public static void main(String[] args) {
        System.out.println(Apple.getAppleInstance());
        System.out.println(Apple.getAppleInstance());
    }
}

plugins {
    id 'java'
    id "io.freefair.lombok" version "6.4.1"
}

group = 'org.wesome'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = JavaVersion.VERSION_1_8

configurations {
    compileOnly {
        extendsFrom annotationProcessor
    }
}

repositories {
    mavenCentral()
}

dependencies {
    testImplementation 'org.junit.jupiter:junit-jupiter:5.6.2'
}

test {
    useJUnitPlatform()
}