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A quick and easy way to join array elements with a separator (the opposite of split) in Java [duplicate]
(15 answers)
Best way to convert an ArrayList to a string
(27 answers)
What's the simplest way to print a Java array?
(37 answers)
Java function for arrays like PHP's join()?
(24 answers)
Closed 3 years ago.
I have an ArrayList<String> that is added to periodically. What I want to do is to cast the entire ArrayList to a String without doing a loop. Can anybody tell me is it possible without using loop?
Edited:
So we found some solutions, Like
list.stream().collect(Collectors.joining());
Or
String result = String.join(",", list);
or some others as well. Now Just for getting knowledge I put a question which one is the most optimal way for compiler?
You could make a stream out of your list and collect it using joining collector :
list.stream().collect(Collectors.joining());
You can pass the separator to Collectors::joining method for example :
list.stream().collect(Collectors.joining("-"));
Or you can use String::join method :
String result = String.join(",", list);
where , is the separator.
I Believe you can do
String.join(", ", list);
Hope this helps :)
Given some ArrayList<String> s, all you need to use to get a String representation is s.toString().
The format is the following
[element1, element2, element3]
Related
This question already has answers here:
Simplest way to add an item to beginning of an array in Java
(9 answers)
Closed 9 months ago.
I am new to Java and I have an array
int [] A = {140,150,160,170,180,190}
I need to add infinity at the beginning of the array
like so:
int [] A = {inf,140,150,160,170,180,190}
I know from Python to do it like so:
A=[140,150,160,170,180,190]
A=[float('inf')]+A
I need a way to do that in Java as simple as Python without loops
It's important to say I need the array / list(A=[140,150,160,170,180,190]) to be given with the code.
You can use Java ArrayList that implements List interface and has a method add(int,E)
So, you can use something like list.add(0, myObj);.
This question already has answers here:
Converting Array to List
(9 answers)
Retrieving a List from a java.util.stream.Stream in Java 8
(15 answers)
Closed 3 years ago.
still very new to Java, my apologies if this has appeared before.
Basically here is the original code
public static MarketType[] convert(final String[] values) {
return ofNullable(values).map(v -> Stream.of(values))
.orElse(Stream.empty())
.map(v -> getMarketType(v))
.toArray(MarketType[]::new);
}
Since other functions changed, I really need the return type to be List<MarketType> instead of MarketType[], but is there any way that can achieve this with the minimal amount of modification for the original code?
I have been trying to put different things in the toArray function but nothing really worked.
Any help appreciated!
This question already has answers here:
How to use subList()
(6 answers)
Closed 3 years ago.
I want to pass an array as argument to a function without first element.
I came up with this solution, but I'm wondering if there are better ways to it.
List<Integer> numbers = new ArrayList<>();
//... in the meantime numbers is an array that contain 1000 elements;
numbers.remove(0);
myFunction(numbers)
You can use subList(firstElement, lastElement); method.
Here please check javadoc.
This question already has answers here:
How can I check if a single character appears in a string?
(16 answers)
Closed 9 years ago.
I have a string like :
"\"[\"a\",\"b\", \"c\"]\""
How to convert this to a list of strings
Could you suggest me a nice way of doing it in Java?
str.contains("c") does this job. However did not you think to consult String class documentation first?
Use contains():
if (str.contains("\"c\""))
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
In Java, how can I test if an Array contains a certain value?
I want to check for a string S whether it is present in string array or not. Is there any direct method to do so ?
EDIT
If the answer excludes the use of List then that would be better.
There are a couple of ways to accomplish this using the Arrays utility class.
If the array is not sorted:
java.util.Arrays.asList(theArray).indexOf(o)
If the array is sorted, you can make use of a binary search for performance:
java.util.Arrays.binarySearch(theArray, o)
See here Where is Java's Array indexOf?
You can convert it to List and check: Arrays.asList(arrayVariable).contains(S)