How Dependency Injection Design Patterns in Java work?

• Identify dependencies:
  • Analyze the classes in your application to determine which objects they rely on to function. These objects are their dependencies.
  • Define clear interfaces or abstract classes to represent these dependencies, promoting loose coupling.
• Inject dependencies:
  • Constructor Injection: Pass the dependencies as arguments to the class’s constructor. This makes them mandatory for object creation and ensures immutability.
  • Setter Injection: Provide setter methods to set the dependencies after object creation. This offers more flexibility but can make the class mutable.
• Inversion of control(IOC): 
  • Employ an IoC container or framework to manage the creation and injection of dependencies. This inverts the control flow, as classes no longer create their own dependencies but receive them from the container.
  • Popular IoC containers in Java include Spring, Guice, and PicoContainer.

The dependency Injection Design Pattern in Java, is part of Design Patterns, let suppose that you have a company, that companies dependent on the employees, and the employees is dependent on the company. So here company will be the dependency of the employee, and employee dependency is the company. So this is Dependency Injection.