Item 14: In public classes, use accessor methods, not public fields

1.  If a class is accessible outside its package, provide accessor methods to preserve the flexibility to change the class’s internal representation.

 

2.  If a class is package-private or is a private nested class, there is nothing inherently wrong with exposing its data fields. If a change in representation becomes desirable, you can make the change without touching any code outside the package or the outer class.

 

3.  The decision to expose the internals of the Dimension class resulted in a serious performance problem that is still with us today.

 

4.  In summary, public classes should never expose mutable fields. It is less harmful, though still questionable, for public classes to expose immutable fields.