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public class Up extends Object { public static int w; public int x;

PRIMO ESERCIZIO (del 26-5-2004) Mostrare l'evoluzione dello stato (ambiente di classi, heap, pila, System.out) dopo ciascuna istruzione del main:. public class Up extends Object { public static int w; public int x; public void met1() {w=x+4; x=x+1;} {x=3;} }

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public class Up extends Object { public static int w; public int x;

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  1. PRIMO ESERCIZIO (del 26-5-2004) Mostrare l'evoluzione dello stato (ambiente di classi, heap, pila, System.out) dopo ciascuna istruzione del main: public class Up extends Object { public static int w; public int x; public void met1() {w=x+4; x=x+1;} {x=3;} } public class Down extends Up { public Up y; public void met2() {y=new Down(); y.x=x+1; y.met1();} public void met1() {x=x+w; w=0;} {x=w;} } public class Princ extends Object { public static void main() { Up p1 = new Up(); p1.w = p1.x + 1; p1.met1(); Down p2 = new Down(); p2.met2(); } }

  2. Ambiente delle classi 0 Nome classe Classe ereditata static non static Princ Object Down Up m2 3 Up Object 1 2 m1 Object

  3. Ambiente delle classi 0 Descrmet1 = <-, {w=x+4; x=x+1; , Up> DescrUp = <-, {x=3;}, Up> Descrmet2 = <-, {y=new Down(); y.x=x+1; y.met1();}, Down> Descr'met1 = <-, {x=x+w; w=0;}, Down> DescrDown = <-, {x=3;x=w;}, Down>

  4. Princ Pila dei Frames vuota! Stato iniziale: <0 , s0 , x0 >

  5. Prima Istruzione del main: Up p1 = new Up(); < Up p1 = new Up();,0 , s0 , x0 > com < 0 , s1 , x1 > Princ Up p1 l1 l1 m1' x1 s1

  6. Seconda Istruzione del main: p1.w = p1.x + 1; < p1.w = p1.x+1; , 0 , s1 , x1 > com < 1 , s1 , x1 > Modifica solo l'ambiente delle classi. Frame delle variabili statiche di UP: 1 1'

  7. Terza Istruzione del main: p1.met1(); < p1.met1(); , 1 , s1 , x1 > com < 2 , s1 , x2 > Modifica l'ambiente delle classi e l'heap. m1'(met1) = < -, {w=x+4; x=x+1}, l1 > Up 1' 1'' l1 m1' x2

  8. Princ p1 p2 l1 l2 s2 Quarta Istruzione del main: Down p2 = new Down(); < Down p2 = new Down(); , 2 , s1 , x2 > com < 2 , s2 , x3 > x3 Up l1 m1' Down l2 m2' x=3; x=w;

  9. Quinta Istruzione del main: p2.met2(); < p2.met2(); , 2 , s2, x3 > com < 3 , s2 , x4> m2'(met2) = < -, {y = new Down(); y.x=x+1; y.met1()}, l2 > l1 /// Down y.x = x+1; l2 m2' In l2 x vale 7 l3 Down l3 m2'' x4'

  10. Quinta Istruzione del main: p2.met2(); < p2.met2(); , 2 , s2, x3 > com < 3 , s2 , x4> m2'(met2) = < -, {y = new Down(); y.x=x+1; y.met1()}, l2 > l1 /// m2''(met1) = < -, {x=x+w; w=0}, l3 > Down x = x + w; l2 m2' 8 7 Infine viene modificato l'ambiente delle classi: l3 Down m2'' 1'' 1''' x4

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