Mixing
return n'th value and key from a hash map in java
For my schooling I have to write a programm, which read and return costumer value from data. To do that, I have created an double hash map. In the inner, i have mapped for example, keys like name, to values like chris. The outer map is for mapping the inner maps, to the costumers name.
To create a list of the accessible files/costumers, I have created that code:
for (HashMap<String, String> file: output.MapForFileMaps.values())
{
h = h + 1;
if (fileRequest == h)
{
requestIsListet = true;
for (String key: file.keySet())
{
p = p + 1;
System.out.println("Press " + p + " for " + key);
}
}
}
Question: Could I reach directly that part of the hash map, which is needed, by asking for the value or key of the hash map on the n`th place?
Current Problem is, that I want to check wheather the input is connected to a accessible part of the map, or not. So I could return this area of code by an while loop, while request is not available.
java
asked Nov 20 '18 at 14:32
ChrisChris
82
add a comment |
For my schooling I have to write a programm, which read and return costumer value from data. To do that, I have created an double hash map. In the inner, i have mapped for example, keys like name, to values like chris. The outer map is for mapping the inner maps, to the costumers name.
To create a list of the accessible files/costumers, I have created that code:
for (HashMap<String, String> file: output.MapForFileMaps.values())
{
h = h + 1;
if (fileRequest == h)
{
requestIsListet = true;
for (String key: file.keySet())
{
p = p + 1;
System.out.println("Press " + p + " for " + key);
}
}
}
Question: Could I reach directly that part of the hash map, which is needed, by asking for the value or key of the hash map on the n`th place?
Current Problem is, that I want to check wheather the input is connected to a accessible part of the map, or not. So I could return this area of code by an while loop, while request is not available.
java
asked Nov 20 '18 at 14:32
ChrisChris
82
3
There is no guarantee the nth value is going to be the same over multiple iterations for a HashMap. See: stackoverflow.com/questions/2144776/…
– Compass
Nov 20 '18 at 14:37
2
It seems you're using wrong data structure for the problem because, by definition, there is no Nth key/value in hash map.
– TheJavaGuy-Ivan Milosavljević
Nov 20 '18 at 14:38
What’s wrong with designing a properCustomerclass with instance variables (fields) for name, etc.? In case it helps you. aLinkedHashMapmaintains insertion order, so you may use its iterator to count to the nth inserted item (provided that no item has later been removed again).
– Ole V.V.
Nov 20 '18 at 15:09
add a comment |
For my schooling I have to write a programm, which read and return costumer value from data. To do that, I have created an double hash map. In the inner, i have mapped for example, keys like name, to values like chris. The outer map is for mapping the inner maps, to the costumers name.
To create a list of the accessible files/costumers, I have created that code:
for (HashMap<String, String> file: output.MapForFileMaps.values())
{
h = h + 1;
if (fileRequest == h)
{
requestIsListet = true;
for (String key: file.keySet())
{
p = p + 1;
System.out.println("Press " + p + " for " + key);
}
}
}
Question: Could I reach directly that part of the hash map, which is needed, by asking for the value or key of the hash map on the n`th place?
Current Problem is, that I want to check wheather the input is connected to a accessible part of the map, or not. So I could return this area of code by an while loop, while request is not available.
java
asked Nov 20 '18 at 14:32
ChrisChris
82
For my schooling I have to write a programm, which read and return costumer value from data. To do that, I have created an double hash map. In the inner, i have mapped for example, keys like name, to values like chris. The outer map is for mapping the inner maps, to the costumers name.
To create a list of the accessible files/costumers, I have created that code:
for (HashMap<String, String> file: output.MapForFileMaps.values())
{
h = h + 1;
if (fileRequest == h)
{
requestIsListet = true;
for (String key: file.keySet())
{
p = p + 1;
System.out.println("Press " + p + " for " + key);
}
}
}
Question: Could I reach directly that part of the hash map, which is needed, by asking for the value or key of the hash map on the n`th place?
Current Problem is, that I want to check wheather the input is connected to a accessible part of the map, or not. So I could return this area of code by an while loop, while request is not available.
java
java
asked Nov 20 '18 at 14:32
ChrisChris
82
asked Nov 20 '18 at 14:32
ChrisChris
82
asked Nov 20 '18 at 14:32
ChrisChris
82
asked Nov 20 '18 at 14:32
ChrisChris
82
asked Nov 20 '18 at 14:32
ChrisChris
82
82
3
There is no guarantee the nth value is going to be the same over multiple iterations for a HashMap. See: stackoverflow.com/questions/2144776/…
– Compass
Nov 20 '18 at 14:37
2
It seems you're using wrong data structure for the problem because, by definition, there is no Nth key/value in hash map.
– TheJavaGuy-Ivan Milosavljević
Nov 20 '18 at 14:38
What’s wrong with designing a properCustomerclass with instance variables (fields) for name, etc.? In case it helps you. aLinkedHashMapmaintains insertion order, so you may use its iterator to count to the nth inserted item (provided that no item has later been removed again).
– Ole V.V.
Nov 20 '18 at 15:09
add a comment |
3
There is no guarantee the nth value is going to be the same over multiple iterations for a HashMap. See: stackoverflow.com/questions/2144776/…
– Compass
Nov 20 '18 at 14:37
2
It seems you're using wrong data structure for the problem because, by definition, there is no Nth key/value in hash map.
– TheJavaGuy-Ivan Milosavljević
Nov 20 '18 at 14:38
What’s wrong with designing a properCustomerclass with instance variables (fields) for name, etc.? In case it helps you. aLinkedHashMapmaintains insertion order, so you may use its iterator to count to the nth inserted item (provided that no item has later been removed again).
– Ole V.V.
Nov 20 '18 at 15:09
3
3
There is no guarantee the nth value is going to be the same over multiple iterations for a HashMap. See: stackoverflow.com/questions/2144776/…
– Compass
Nov 20 '18 at 14:37
There is no guarantee the nth value is going to be the same over multiple iterations for a HashMap. See: stackoverflow.com/questions/2144776/…
– Compass
Nov 20 '18 at 14:37
2
2
It seems you're using wrong data structure for the problem because, by definition, there is no Nth key/value in hash map.
– TheJavaGuy-Ivan Milosavljević
Nov 20 '18 at 14:38
It seems you're using wrong data structure for the problem because, by definition, there is no Nth key/value in hash map.
– TheJavaGuy-Ivan Milosavljević
Nov 20 '18 at 14:38
What’s wrong with designing a proper
Customer class with instance variables (fields) for name, etc.? In case it helps you. a LinkedHashMap maintains insertion order, so you may use its iterator to count to the nth inserted item (provided that no item has later been removed again).– Ole V.V.
Nov 20 '18 at 15:09
What’s wrong with designing a proper
Customer class with instance variables (fields) for name, etc.? In case it helps you. a LinkedHashMap maintains insertion order, so you may use its iterator to count to the nth inserted item (provided that no item has later been removed again).– Ole V.V.
Nov 20 '18 at 15:09
add a comment |
1 Answer
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Question: Could I reach directly that part of the hash map, which is needed, by asking for the value or key of the hash map on the n`th place?
Answer: You COULD, but it wouldnt be efficcient, Hashmaps store elements based on a hash of the key, so the first inserted element isnt per definition on index 0. You can instead use the key to get the value
Take a look here: https://www.geeksforgeeks.org/internal-working-of-hashmap-java/
answered Nov 20 '18 at 14:37
Teun van der WijstTeun van der Wijst
570315
add a comment |
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1 Answer
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active
oldest
votes
1 Answer
1
active
oldest
votes
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oldest
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active
oldest
votes
Question: Could I reach directly that part of the hash map, which is needed, by asking for the value or key of the hash map on the n`th place?
Answer: You COULD, but it wouldnt be efficcient, Hashmaps store elements based on a hash of the key, so the first inserted element isnt per definition on index 0. You can instead use the key to get the value
Take a look here: https://www.geeksforgeeks.org/internal-working-of-hashmap-java/
answered Nov 20 '18 at 14:37
Teun van der WijstTeun van der Wijst
570315
add a comment |
Question: Could I reach directly that part of the hash map, which is needed, by asking for the value or key of the hash map on the n`th place?
Answer: You COULD, but it wouldnt be efficcient, Hashmaps store elements based on a hash of the key, so the first inserted element isnt per definition on index 0. You can instead use the key to get the value
Take a look here: https://www.geeksforgeeks.org/internal-working-of-hashmap-java/
answered Nov 20 '18 at 14:37
Teun van der WijstTeun van der Wijst
570315
add a comment |
Question: Could I reach directly that part of the hash map, which is needed, by asking for the value or key of the hash map on the n`th place?
Answer: You COULD, but it wouldnt be efficcient, Hashmaps store elements based on a hash of the key, so the first inserted element isnt per definition on index 0. You can instead use the key to get the value
Take a look here: https://www.geeksforgeeks.org/internal-working-of-hashmap-java/
answered Nov 20 '18 at 14:37
Teun van der WijstTeun van der Wijst
570315
Question: Could I reach directly that part of the hash map, which is needed, by asking for the value or key of the hash map on the n`th place?
Answer: You COULD, but it wouldnt be efficcient, Hashmaps store elements based on a hash of the key, so the first inserted element isnt per definition on index 0. You can instead use the key to get the value
Take a look here: https://www.geeksforgeeks.org/internal-working-of-hashmap-java/
answered Nov 20 '18 at 14:37
Teun van der WijstTeun van der Wijst
570315
answered Nov 20 '18 at 14:37
Teun van der WijstTeun van der Wijst
570315
answered Nov 20 '18 at 14:37
Teun van der WijstTeun van der Wijst
570315
answered Nov 20 '18 at 14:37
Teun van der WijstTeun van der Wijst
570315
570315
add a comment |
add a comment |
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3
There is no guarantee the nth value is going to be the same over multiple iterations for a HashMap. See: stackoverflow.com/questions/2144776/…
– Compass
Nov 20 '18 at 14:37
2
It seems you're using wrong data structure for the problem because, by definition, there is no Nth key/value in hash map.
– TheJavaGuy-Ivan Milosavljević
Nov 20 '18 at 14:38
What’s wrong with designing a proper
Customerclass with instance variables (fields) for name, etc.? In case it helps you. aLinkedHashMapmaintains insertion order, so you may use its iterator to count to the nth inserted item (provided that no item has later been removed again).– Ole V.V.
Nov 20 '18 at 15:09