ErrorHandlingAndNullChecks Java8 Way

Sample.json

[
  {
    "EventID": "1",
    "EventName": "login",
    "CommonAttributes": {
      "Location": "NY",
      "Country": "US"
    }
  },
  {
    "EventID": "2",
    "EventName": "click_on_ad",
    "CommonAttributes": {
      "Location": "NY",
      "Country": "US"
    },
    "Properties": {
      "ShowImpression": true,
      "LoginRequired": true,
      "UnitPrice": 4.56
    }
  },
  {
    "EventID": "3",
    "EventName": "click_on_list",
    "CommonAttributes": {
      "Location": "NY",
      "Country": "US"
    },
    "Properties": {
      "LoginRequired": true,
      "UnitPrice": 9.18
    }
  },
  {
    "EventID": "4",
    "EventName": "click_on_ad",
    "CommonAttributes": {
      "Location": "NY",
      "Country": "US"
    },
    "Properties": {
      "ShowImpression": true,
      "LoginRequired": false,
      "UnitPrice": 5.78
    }
  },
  {
    "EventID": "5",
    "EventName": "logout",
    "CommonAttributes": {
      "Location": "NY",
      "Country": "US"
    }
  }
]

WithExplicitNullCheck.java

package programming.imperative;

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;


class CommonAttributes {
    @JsonProperty("Location")
    private String location;
    @JsonProperty("Country")
    private String country;

    public String getLocation() {
        return location;
    }

    public String getCountry() {
        return country;
    }
}

class Properties {
    @JsonProperty("ShowImpression")
    private boolean showImpression;
    @JsonProperty("LoginRequired")
    private boolean loginRequired;
    @JsonProperty("UnitPrice")
    private double unitPrice;

    public Boolean isShowImpression() {
        return showImpression;
    }

    public Boolean isLoginRequired() {
        return loginRequired;
    }

    public Double getUnitPrice() {
        return unitPrice;
    }
}

class Event {
    @JsonProperty("EventID")
    private String eventID;
    @JsonProperty("EventName")
    private String eventName;
    @JsonProperty("CommonAttributes")
    private CommonAttributes commonAttributes;
    @JsonProperty("Properties")
    private Properties properties;

    public String getEventID() {
        return eventID;
    }

    public String getEventName() {
        return eventName;
    }

    public CommonAttributes getCommonAttributes() {
        return commonAttributes;
    }

    public Properties getProperties() {
        return properties;
    }
}

public class WithExplicitNullCheck {

    public static void main(String[] args) {
        String fileName = "src/main/resources/Sample.json";
        try {
            final Event[] events = new ObjectMapper().readValue(new File(fileName), Event[].class);
            List<Double> doublePrices = new ArrayList<>();
            for (Event event : events) {
                if (event.getProperties() != null) {
                    doublePrices.add(event.getProperties().getUnitPrice());
                }
            }
            System.out.println(doublePrices);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

WithoutExplicitNullCheck.java

package programming.functional;

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

class CommonAttributes {
    @JsonProperty("Location")
    private String location;
    @JsonProperty("Country")
    private String country;

    public String getLocation() {
        return location;
    }

    public String getCountry() {
        return country;
    }
}

class Properties {
    @JsonProperty("ShowImpression")
    private boolean showImpression;
    @JsonProperty("LoginRequired")
    private boolean loginRequired;
    @JsonProperty("UnitPrice")
    private double unitPrice;

    public Boolean isShowImpression() {
        return showImpression;
    }

    public Boolean isLoginRequired() {
        return loginRequired;
    }

    public Double getUnitPrice() {
        return unitPrice;
    }
}

class Event {
    @JsonProperty("EventID")
    private String eventID;
    @JsonProperty("EventName")
    private String eventName;
    @JsonProperty("CommonAttributes")
    private CommonAttributes commonAttributes;
    @JsonProperty("Properties")
    private Properties properties;

    public String getEventID() {
        return eventID;
    }

    public String getEventName() {
        return eventName;
    }

    public CommonAttributes getCommonAttributes() {
        return commonAttributes;
    }

    public Optional<Properties> getProperties() {
        return Optional.ofNullable(properties);
    }
}

public class WithoutExplicitNullCheck {

    public static void main(String[] args) {
        String fileName = "src/main/resources/Sample.json";
        try {
            final Event[] events = new ObjectMapper().readValue(new File(fileName), Event[].class);
            final List<Double> collect = Arrays.stream(events)
                    .flatMap(event -> event.getProperties().stream())
                    .map(Properties::getUnitPrice)
                    .collect(Collectors.toList());
            System.out.println(collect);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}