It makes the construction of similar objects a lot easier.
For this example, let’s assume that a ComplexPerson object represents a human that has parents, and has attributes such as age, name, etc.
ComplexPerson.Builder jimJaneFamily = ComplexPerson.builder().getParent(jimReference,janeReference);
To create new children from the same template, you would just use the builder “jimJaneFamily” object, adjust the new attributes and call build. A new builder object isn’t necessary as that the modifiable fields are overwritten and the builder is no longer relevant after the build method is called. Reusing the builder object looks a lot cleaner compared to new initializations per new object.
That’s pretty cool.