Effective Java 第14条：在公有类中使用访问方法而非公有域
退化类(Degenerate classes): 没有什么作用，只是用来集中实例域
// Degenerate classes like this should not be public!
class Point {
public double x;
public double y;
}
用包含私有域和公有访问方法(getter)的类代替
// Encapsulation of data by accessor methods and mutators
class Point {
private double x;
private double y;
public Point(double x, double y) {
this.x = x;
this.y = y;
}
public double getX() {
return x;
}
public double getY() {
return y;
}
public void setX(double x) {
this.x = x;
}
public void setY(double y) {
this.y = y;
}
}