"Turn" hashmap shallow copy and deep copy--good

Original URL: http://canofy.iteye.com/blog/258790

Java deep copy and shallow copy

2. Shallow copy and deep copy
4. //Shallow copy: All variables of the copied object contain the same value as the original object, and all references to other objects still point to the original object.
6. //In other words, shallow copy simply duplicates the object being considered, not the object it refers to.
8. //Deep copy: All the variables of the copied object contain the same values as the original object, removing those variables that refer to other objects.
10. The variables that refer to other objects will point to new objects that have been copied, not those that are already referenced.
12. //In other words, deep copy copies the objects that are referenced by the object being copied again.
14. ///1, Direct Assignment (outside the string is a shallow copy)
16. //2, using the constructor (deep copy)
18. //3, using the Clone () method (deep copy)
22. //String (not understood without Colne () method)
24. String s="SSS";
26. String T=s; //Deep copy
28. String y=new string (s); //Deep copy
30. System.out.println ("s:" +s+"T:" +t+"y:" +y ");
32. t="TTT";
34. y="yyy";
36. System.out.println ("s:" +s+"T:" +t+"y:" +y ");
40. //Array
42. String[] ss={"111","222","333"};
44. String[] TT=SS; //Shallow copy
46. String[] ww= (string[]) ss.clone (); //Deep copy
48. System.out.println ("ss:" +ss[1]+"tt:" +tt[1]+"ww:" +ww[1]);
50. tt[1]="2t2";
52. ww[1]="2w2";
54. System.out.println ("ss:" +ss[1]+"tt:" +tt[1]+"ww:" +ww[1]);
60. //list List
62. ArrayList a=New ArrayList ();
64. For (int i=0;i<10;i++) {
66. A.add (string.valueof (i+1));
68. }
70. ArrayList B=a; //Shallow copy
72. ArrayList c=New ArrayList (a); Deep copy
74. ArrayList d= (ArrayList) A.clone (); //Deep copy
76. System.out.println ("A:" +a.get (1) +"B:" +b.get (1) +"C:" +c.get (1) +"D:" +d.get (1));
78. B.set (1, "BBB");
80. C.set (1, "CCC");
82. System.out.println ("A:" +a.get (1) +"B:" +b.get (1) +"C:" +c.get (1) +"D:" +d.get (1));
86. //hashmap
88. HashMap h=New HashMap ();
90. H.put ("1", "HHH");
92. HashMap m=h; //Shallow copy
94. HashMap p=New HashMap (h); Deep copy
96. HashMap n= (HASHMAP) H.clone (); //Deep copy
98. System.out.println ("H:" +h.get ("1") +"M:" +m.get ("1") +"P:" +p.get ("1") + "N:" +n.get (  "1"));
100. M.put ("1", "MMM");
102. P.put ("1","PPP");
104. N.put ("1", "nnn");
106. System.out.println ("H:" +h.get ("1") +"M:" +m.get ("1") +"P:" +p.get ("1") + "N:" +n.get (  "1"));

"Turn" hashmap shallow copy and deep copy--good