How to convert a List to variable argument parameter java
JavaListVariadic FunctionsJava Problem Overview
I have a method which takes a variable length string (String...) as parameter. I have a List<String> with me. How can I pass this to the method as argument?
Java Solutions
Solution 1 - Java
String... equals a String[]
So just convert your list to a String[] and you should be fine.
Solution 2 - Java
String ... and String[] are identical If you convert your list to array.
using
Foo[] array = list.toArray(new Foo[list.size()]);
or
Foo[] array = new Foo[list.size()];
list.toArray(array);
then use that array as String ... argument to function.
Solution 3 - Java
You can use stream in java 8.
String[] array = list.stream().toArray(String[]::new);
Then the array can be used in the ...args position.
Solution 4 - Java
in case of long (primitive value)
long[] longArray = list.stream().mapToLong(o->g.getValue()).toArray();
when getValue() returns a long type
Solution 5 - Java
For Java > 8
You can very well use the toArray method very simply, as in:
String[] myParams = myList.toArray(String[]::new);
Streaming becomes really interesting when the elements of the List must be transformed, filtered or else before being converted to Array:
String[] myMappedAndFilteredParams = myList.stream()
.map(param -> param + "some_added_stuff")
.filter(param -> param.contains("some very important info"))
.collect(toList())
.toArray(String[]::new);