Why do people make fields private in java?

Answer 1

To prevent a subclass from inheriting those.

A subclass will inherit public and protected members of it's superclass. Package-private members will only be inherited for subclasses in the same package.

consider:

class car{

static public numberBuilt = 0;

public car(){

numberBuilt++;}

/**********/

class raceCar{

public raceCar(){

numberBuilt++;}}

/*

* If numberBuilt had been declared as private, an error would be caused

* by raceCar's use of numberBuilt, influencing a programmer to make a new

* static numberBuilt variable for CarRacecar and other extensions of Car, and

* showing that other things are deprecated. */