FilesExpand file tree

master

/

cache_right_and_wrong.java

Copy path

Blame

More file actions

Blame

More file actions

Latest commit

 

History

History

History

64 lines (48 loc) · 1.3 KB

master

/

cache_right_and_wrong.java

Copy path

Top

File metadata and controls

• Code
• Blame

64 lines (48 loc) · 1.3 KB

Raw

Copy raw file

Download raw file

Open symbols panel

Edit and raw actions

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

package doc;

import org.mapdb.DB;

import org.mapdb.DBMaker;

import java.util.Map;

public class cache_right_and_wrong {

static class Person implements Cloneable{

private String name;

private int age;

public void setName(String name) {

this.name = name;

}

public void setAge(int age) {

this.age = age;

}

public Person clone(){

Person ret = new Person();

ret.age = age;

ret.name = name;

return ret;

}

}

public static void main(String[] args) {

DB db = DBMaker

.memoryDB()

.cacheHardRefEnable()

.make();

Map<String, Person> map =

db.hashMap("map");

//a

//wrong

Person person = new Person();

map.put("John", person);

person.setName("John");

//right

person = new Person();

person.setName("John");

map.put("John", person);

//wrong

person = map.get("John");

person.setAge(15);

//right, create copy which is modified and inserted

person = map.get("John");

person = person.clone(); //defensive copy

person.setAge(15);

map.put("John", person);

//z

}

}