INHERITANCE AND MEMBER ACCESSIBILITY

What?
- which data and methods can be accessed from where
How?
- rules which apply equally to all members, data or methods, class or instance

Example Hierarchy:
        Grandparent
   Mother         Uncle
Child

Each class has one data members
- public
- named with first letter of class and type, 
  e.g. g_pub is Grandparent's data member

What?
- inheriting public
How?
- always inherited from ancestors
Examples:
- Draw class diagrams, public data only
- What's legal?
  public void childMethod() {
      g_pub = "cg"; => yes
      m_pub = "cm"; => yes
      c_pub = "cc"; => yes
      u_pub = "cu"; => no
  }
  public void momMethod() {
      g_pub = "mg"; => yes
      m_pub = "mm"; => yes
      c_pub = "mc"; => no
      u_pub = "mu"; => no
  }
  public void uncMethod() {
      g_pub = "ug"; => yes
      m_pub = "um"; => no
      c_pub = "uc"; => no
      u_pub = "uu"; => yes
  }
  public void grandMethod() {
      g_pub = "gg"; => yes
      m_pub = "gm"; => no
      c_pub = "cm"; => no
      u_pub = "cu"; => no
  }

What?
- accessing public
How?
- accessible from any object or class, regardless of inheritance
Example:
- If it's always accessible, why did we have problems above?
  => because we were treating it as our own data; always accessible means it can 
     be used directly when associated with a class or instance (depending on its 
     type)
Example:
  grandMethod() {
      Child gc = new Child();
      gc.c_pub = "gc";

      Mother gm = new Mother();
      gm.m_pub = "gm";

      Uncle gu = new Uncle();
      gu.u_pub = "gu";

      Grandparent gg = new Grandparent();
      gg.u_pub = "gg";
  }
  - How would we change this for childMethod? momMethod? uncleMethod?
    => They can all be exactly the same.
  - Draw a chart
    
What?
- inheriting private
How?
- not inherited
Example:
- Add private data to our class diagrams, similar naming scheme (using pri)
- What's legal?
  public void childMethod() {
      g_pri = "cg"; => no
      m_pri = "cm"; => no
      c_pri = "cc"; => yes
      u_pri = "cu"; => no
  }
  public void momMethod() {
      g_pri = "mg"; => no
      m_pri = "mm"; => yes
      c_pri = "mc"; => no
      u_pri = "mu"; => no
  }
  public void uncMethod() {
      g_pri = "ug"; => no
      m_pri = "um"; => no
      c_pri = "uc"; => no
      u_pri = "uu"; => yes
  }
  public void grandMethod() {
      g_pri = "gg"; => yes
      m_pri = "gm"; => no
      c_pri = "cm"; => no
      u_pri = "cu"; => no
  }

What?
- accessing private
How?
- never accessible from any outside object or class
Example:
  childMethod() {
      Mother cm = new Mother();
      cm.setPriv("gm");

      Uncle cu = new Uncle();
      cu.setPriv("cu");

      Grandparent cg = new Grandparent();
      cg.setPriv("gg");

      Child cc = new Child();
      cc.c_priv = "gc";
  }
  - How would this change for the others?
    => Draw a chart.

What?
- inheriting protected
What?
- always inherited by people who directly or indirectly extend you
Example:
- Add protected data to our class diagrams, similar naming scheme (using pro)
- What's legal?
  public void childMethod() {
      g_pro = "cg"; => yes
      m_pro = "cm"; => yes
      c_pro = "cc"; => yes
      u_pro = "cu"; => no
  }
  public void momMethod() {
      g_pro = "mg"; => yes
      m_pro = "mm"; => yes
      c_pro = "mc"; => no
      u_pro = "mu"; => no
  }
  public void uncMethod() {
      g_pro = "ug"; => yes
      m_pro = "um"; => no
      c_pro = "uc"; => no
      u_pro = "uu"; => yes
  }
  public void grandMethod() {
      g_pro = "gg"; => yes
      m_pro = "gm"; => no
      c_pro = "cm"; => no
      u_pro = "cu"; => no
  }

What?
- accessing protected
How?
- a method can only access members that
  - belong to its own same class
  - belong to its ancestor classes
Example:
  momMethod() {
      Grandparent mg = new Grandparent();
      mg.g_pro = "gg";

      Uncle mu = new Uncle();
      mu.setPriv("mu");

      Mother mm = new Mother();
      mm.m_pro = "gm";

      Child mc = new Child();
      mc.setPriv("mc");
  }
  - How would this change for the others?
    => Draw a chart

What?
- default visibility  
How?
- package: component is accessible from any method of a class that belongs to the 
  same package as the component's class
- not used in this course