NAVNEETOJHA

import java.io.*;

class BasicSingleton implements Serializable
{
  // cannot new this class, however
  // * instance can be created deliberately (reflection)
  // * instance can be created accidentally (serialization)
  private BasicSingleton() {
    System.out.println("Singleton is initializing");

NAVNEETOJHA

import org.apache.commons.lang3.SerializationUtils;

import java.io.Serializable;

// some libraries use reflection (no need for Serializable)
class Foo implements Serializable
{
  public int stuff;
  public String whatever;

NAVNEETOJHA

import java.util.Arrays;

// Cloneable is a marker interface
class Address implements Cloneable {
  public String streetName;
  public int houseNumber;

  public Address(String streetName, int houseNumber)

NAVNEETOJHA

class Address
{
  public String streetAddress, city, country;

  public Address(String streetAddress, String city, String country)
  {
    this.streetAddress = streetAddress;
    this.city = city;
    this.country = country;

NAVNEETOJHA

class Person
{
  // address
  public String streetAddress, postcode, city;

  // employment
  public String companyName, position;
  public int annualIncome;

NAVNEETOJHA

enum CoordinateSystem
{
  CARTESIAN,
  POLAR
}

class Point
{
  private double x, y;

NAVNEETOJHA

class Person
{
  // address
  public String streetAddress, postcode, city;

  // employment
  public String companyName, position;
  public int annualIncome;

NAVNEETOJHA

import java.util.ArrayList;
import java.util.Collections;

class HtmlElement
{
  public String name, text;
  public ArrayList<HtmlElement> elements = new ArrayList<HtmlElement>();
  private final int indentSize = 2;

NAVNEETOJHA

import org.javatuples.Triplet;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;

// A. High-level modules should not depend on low-level modules. 
// Both should depend on abstractions.

NAVNEETOJHA

class Document
{
}

interface Machine
{
  void print(Document d);
  void fax(Document d) throws Exception;
  void scan(Document d) throws Exception;