invariant

encapsulation


life cycle of an object
    1. created
        - on the heap
    2. (fields cannot be modified)
       methods are invoked
    3. destroyed?

class A { ...  .... }

A aobj = new A();   // 1.

  1000        6246
  1.          2.          aobj
--|      |----|       |---|1000|----------------
      \-----/

aobj = new A();     // 2.

  1000        6246
  1.          2.          aobj
--|      |----|       |---|6246|----------------

aobj = null;



A aobj = new A();   // 1.
A bobj = aobj;
aobj = new A();     // 2.


A aobj = new A();   // 1.
aobj = new A();     // 2.


not Java: pointers
Java:     references



garbage collection


(new A()).f();

list.add(new A());


class A {
    int val;
    String text;
    double dval1;
    Double dval2;
}

   aobj
   val text dval1 dval2    1234      6789
---|5  |1234|1.457|6789|---|"foo"|---|1.457|---------------------

A aobj = new A();
aobj.val   = 5;
aobj.text  = "foo";
aobj.dval1 = 1.457;
aobj.dval2 = new Double(1.457);


int[]     ia1 = new int[3];
Integer[] ia2 = new Integer[3];

 ia1       addr1 ia2                     addr3    addr2
-|1|2|3|---|1|---|addr1|addr2|addr3|-----|3|------|2|-----------------------------------