How to Use Guava BiMap for Inverse Map Lookup

A BiMap is useful in scenarios where you need to look up data in both directions.

For example, if you have a mapping between employee IDs and names, and you want to quickly retrieve an employee’s ID based on their name or vice versa, a BiMap can provide this functionality.

Guava provides an implementation of the BiMap interface called HashBiMap. Let’s see you can use it.

Convert Java Object to Map

You can use ObjectMapper.convertValue to convert a java object to a java map.

The convertValue method in the ObjectMapper class allows you to convert a Java object of one type to another type, without the need for explicit serialization and deserialization steps.

This method takes two parameters: the source object and the target type (specified as a JavaType or TypeReference).

Let’s consider a simple example to demonstrate the usage of convertValue. Suppose we have a Person class, and we want to convert an instance of Person to a Map<String, Object> representation:

Use Guava Multiset to Count the Occurences of Elements in a List

The Multiset class in Google’s Guava library provides a powerful data structure that extends the capabilities of a traditional Set by allowing multiple occurrences of the same element. This makes Multiset particularly useful for counting elements and solving problems where element frequency matters.

How to Use Guava Stopwatch

The Stopwatch class in Google’s Guava library is a powerful utility for measuring elapsed time in our applications. It simplifies the process of tracking how long operations take, which can be useful for performance monitoring, debugging, and optimization.

Ignoring Null Fields with @JsonInclude

The @JsonInclude annotation is used to specify whether fields with null values should be included in the JSON output. By applying this annotation to fields or at the class level, we can control how Jackson handles null fields during serialization.

Map Field Names Using @JsonAlias

The @JsonAlias annotation is used to specify alternate names for properties during deserialization. This allows us to map properties from JSON data to corresponding fields in our Java class, even if the property names don’t match exactly.

Control the Field Order in Serialized JSON Using @JsonPropertyOrder

Jackson provides a @JsonPropertyOrder annotation to specify the order of fields(possibly partial) on serialization. Fields included in annotation declaration will be serialized first in defined order, followed by any fields not included in the definition. This is very helpful when you want to ensure that some fields are output before other fields