测试用例：
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package
test;
import
org.junit.Test;
import
po.Person;
import
java.util.HashMap;
import
java.util.IdentityHashMap;
import
java.util.Map;
/**
* Created by Administrator on 2015/9/16.
*/
public
class
TestMap {
/**
* map插入相同key问题，value会不会覆盖
*/
@Test
public
void
testMap(){
//HashMap中key的内容相同，则覆盖
Map<String,Object> map1 =
new
HashMap<>();
map1.put(
"张三"
,
1
);
map1.put(
"张三"
,
2
);
map1.put(
new
String(
"张三"
),
3
);
//根据String特性，这三条内容相同，前两条地址相同
map1.put(
"李四"
,
4
);
for
(String s : map1.keySet()) {
System.out.println(s+
"======"
+map1.get(s));
}
/** 结果
* 张三======3
李四======4
*/
System.out.println(
"====================================="
);
//IdentityHashMap中key的内存地址必须完全相同才会覆盖
Map<String,Object> map2 =
new
IdentityHashMap<>();
map2.put(
"张三"
,
1
);
map2.put(
"张三"
,
2
);
map2.put(
new
String(
"张三"
),
3
);
//
map2.put(
"李四"
,
4
);
for
(String s : map2.keySet()) {
System.out.println(s+
"===="
+map2.get(s));
}
/**
* 李四====4
张三====2
张三====3
*/
System.out.println(
"====================================="
);
Map<Person,Object> map3 =
new
IdentityHashMap<>();
map3.put(
new
Person(
"张三"
,
11
),
1
);
map3.put(
new
Person(
"张三"
,
11
),
3
);
map3.put(
new
Person(
"李四"
,
11
),
4
);
for
(Person s : map3.keySet()) {
System.out.println(s.toString()+
"===="
+map3.get(s));
}
/**
* po.Person@165474cf====1
po.Person@3ff2caf4====4
po.Person@2c0cd7d====3
*/
System.out.println(
"====================================="
);
Person person =
new
Person(
"张三"
,
11
);
Person person2 =
new
Person(
"张三"
,
11
);
System.out.println(person.equals(person2));
}
}
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package
po;
/**
* Created by Administrator on 2015/9/16.
*/
public
class
Person {
int
id;
String name;
int
age;
@Override
public
String toString() {
return
"Person{"
+
"id="
+ id +
", name='"
+ name + '\
''
+
", age="
+ age +
'}'
;
}
@Override
public
boolean
equals(Object o) {
if
(
this
== o)
return
true
;
if
(o ==
null
|| getClass() != o.getClass())
return
false
;
Person person = (Person) o;
if
(id != person.id)
return
false
;
if
(age != person.age)
return
false
;
return
!(name !=
null
? !name.equals(person.name) : person.name !=
null
);
}
@Override
public
int
hashCode() {
int
result = id;
result =
31
* result + (name !=
null
? name.hashCode() :
0
);
result =
31
* result + age;
return
result;
}
public
Person(String name,
int
age){
this
.name=name;
this
.age=age;
}
}
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本文转自Ryan.Miao博客园博客，原文链接：http://www.cnblogs.com/woshimrf/p/4813664.html，如需转载请自行联系原作者
