Collect list of Integer (List) to map with Java 8 Stream API
I tried to convert a simple List<Integer> to a Map using Java 8 stream API and got the following compile time error:
The method toMap(Function<? super T,? extends K>, Function<? super T,?
extends U>) in the type Collectors is not applicable for the arguments
(Function<Object,Object>, boolean)
My code:
ArrayList<Integer> m_list = new ArrayList<Integer>();
m_list.add(1);
m_list.add(2);
m_list.add(3);
m_list.add(4);
Map<Integer, Boolean> m_map = m_list.stream().collect(
Collectors.toMap(Function.identity(), true));
I also tried the second method below but got the same error.
Map<Integer, Boolean> m_map = m_list.stream().collect(
Collectors.toMap(Integer::intValue, true));
What is the correct way to do this using Java 8 stream API?
arraylist collections java-8 hashmap java-stream
edited Nov 16 '18 at 7:25
Eran
291k37479563
asked Nov 16 '18 at 7:13
UnknownUnknown
4232819
add a comment |
I tried to convert a simple List<Integer> to a Map using Java 8 stream API and got the following compile time error:
The method toMap(Function<? super T,? extends K>, Function<? super T,?
extends U>) in the type Collectors is not applicable for the arguments
(Function<Object,Object>, boolean)
My code:
ArrayList<Integer> m_list = new ArrayList<Integer>();
m_list.add(1);
m_list.add(2);
m_list.add(3);
m_list.add(4);
Map<Integer, Boolean> m_map = m_list.stream().collect(
Collectors.toMap(Function.identity(), true));
I also tried the second method below but got the same error.
Map<Integer, Boolean> m_map = m_list.stream().collect(
Collectors.toMap(Integer::intValue, true));
What is the correct way to do this using Java 8 stream API?
arraylist collections java-8 hashmap java-stream
edited Nov 16 '18 at 7:25
Eran
291k37479563
asked Nov 16 '18 at 7:13
UnknownUnknown
4232819
add a comment |
I tried to convert a simple List<Integer> to a Map using Java 8 stream API and got the following compile time error:
The method toMap(Function<? super T,? extends K>, Function<? super T,?
extends U>) in the type Collectors is not applicable for the arguments
(Function<Object,Object>, boolean)
My code:
ArrayList<Integer> m_list = new ArrayList<Integer>();
m_list.add(1);
m_list.add(2);
m_list.add(3);
m_list.add(4);
Map<Integer, Boolean> m_map = m_list.stream().collect(
Collectors.toMap(Function.identity(), true));
I also tried the second method below but got the same error.
Map<Integer, Boolean> m_map = m_list.stream().collect(
Collectors.toMap(Integer::intValue, true));
What is the correct way to do this using Java 8 stream API?
arraylist collections java-8 hashmap java-stream
edited Nov 16 '18 at 7:25
Eran
291k37479563
asked Nov 16 '18 at 7:13
UnknownUnknown
4232819
I tried to convert a simple List<Integer> to a Map using Java 8 stream API and got the following compile time error:
The method toMap(Function<? super T,? extends K>, Function<? super T,?
extends U>) in the type Collectors is not applicable for the arguments
(Function<Object,Object>, boolean)
My code:
ArrayList<Integer> m_list = new ArrayList<Integer>();
m_list.add(1);
m_list.add(2);
m_list.add(3);
m_list.add(4);
Map<Integer, Boolean> m_map = m_list.stream().collect(
Collectors.toMap(Function.identity(), true));
I also tried the second method below but got the same error.
Map<Integer, Boolean> m_map = m_list.stream().collect(
Collectors.toMap(Integer::intValue, true));
What is the correct way to do this using Java 8 stream API?
arraylist collections java-8 hashmap java-stream
arraylist collections java-8 hashmap java-stream
edited Nov 16 '18 at 7:25
Eran
291k37479563
asked Nov 16 '18 at 7:13
UnknownUnknown
4232819
edited Nov 16 '18 at 7:25
Eran
291k37479563
asked Nov 16 '18 at 7:13
UnknownUnknown
4232819
edited Nov 16 '18 at 7:25
Eran
291k37479563
edited Nov 16 '18 at 7:25
Eran
291k37479563
edited Nov 16 '18 at 7:25
Eran
291k37479563
291k37479563
asked Nov 16 '18 at 7:13
UnknownUnknown
4232819
asked Nov 16 '18 at 7:13
UnknownUnknown
4232819
asked Nov 16 '18 at 7:13
UnknownUnknown
4232819
4232819
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
You are passing a boolean for the value mapper. You should pass a Function<Integer,Boolean>.
It should be:
Map<Integer, Boolean> m_map = m_list.stream().collect(
Collectors.toMap(Function.identity(), e -> true));
answered Nov 16 '18 at 7:13
EranEran
291k37479563
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
You are passing a boolean for the value mapper. You should pass a Function<Integer,Boolean>.
It should be:
Map<Integer, Boolean> m_map = m_list.stream().collect(
Collectors.toMap(Function.identity(), e -> true));
answered Nov 16 '18 at 7:13
EranEran
291k37479563
add a comment |
You are passing a boolean for the value mapper. You should pass a Function<Integer,Boolean>.
It should be:
Map<Integer, Boolean> m_map = m_list.stream().collect(
Collectors.toMap(Function.identity(), e -> true));
answered Nov 16 '18 at 7:13
EranEran
291k37479563
add a comment |
You are passing a boolean for the value mapper. You should pass a Function<Integer,Boolean>.
It should be:
Map<Integer, Boolean> m_map = m_list.stream().collect(
Collectors.toMap(Function.identity(), e -> true));
answered Nov 16 '18 at 7:13
EranEran
291k37479563
You are passing a boolean for the value mapper. You should pass a Function<Integer,Boolean>.
It should be:
Map<Integer, Boolean> m_map = m_list.stream().collect(
Collectors.toMap(Function.identity(), e -> true));
answered Nov 16 '18 at 7:13
EranEran
291k37479563
answered Nov 16 '18 at 7:13
EranEran
291k37479563
answered Nov 16 '18 at 7:13
EranEran
291k37479563
answered Nov 16 '18 at 7:13
EranEran
291k37479563
291k37479563
add a comment |
add a comment |
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