Dependency inversion is a technique that allows your code to decide on what implementation of a method gets called at run time. This maximizes the benefits of late binding. The technique is necessary when the language does not support run time replacement of non-instance functions. For example, Java lacks a mechanism to replace calls to a static method with calls to a different implementation; contrast with Python, where all that's necessary to replace the function call is to bind the name to a different function (reassign the variable holding the function).

Dependency injection is a technique that is intended to help you avoid huge, tangled construction trees that look like this pseudocode:

Dependency inversion or injection is a technique that allows your code to decide on what implementation of a method gets called at run time. This maximizes the benefits of late binding. The technique is necessary when the language does not support run time replacement of non-instance functions. For example, Java lacks a mechanism to replace calls to a static method with calls to a different implementation; contrast with Python, where all that's necessary to replace the function call is to bind the name to a different function (reassign the variable holding the function).

You may also want to take note of inversion of control containers. This is a technique that is intended to help you avoid huge, tangled construction trees that look like this pseudocode:

You should use techniques to solve the problems they're good at solving when you have those problems. Dependency inversion and injection are no different.

Dependency injection is a technique that is intended to help you avoid huge, tangled construction trees that look like this:

Dependency injection is a technique that is intended to help you avoid huge, tangled construction trees that look like this pseudocode: