Arrays.asList(array) in java add unwanted spaces between comma separated string?

Question

I have a string array that I convert to ArrayList and remove an item from it. Then use that updated ArrayList.

Problem Initial Input:

String[] arr = {"467","470","464","410"};
List<String> idList = new LinkedList<>(Arrays.asList(arr));

After converting and removing item it prints

[467, 470, 464]

It adds unwanted leading white spaces between the elements of list, which causes trouble as then I operate on it using

if (idList.toString().contains(userId)) {
      idList.remove(userId); 
}

So if userId="470" and in this list it is " 470", it doesn't match due to white space's issue and code fails.

It tried few things like using integer array instead of string, but it makes no difference.

or

List<String> idList = new LinkedList<>(Arrays.asList(arr));
System.out.println("==>"+idList);

List afterRemovingWhiteSpace = new ArrayList<>();
idList.forEach(e -> afterRemovingWhiteSpace.add(e.trim()));
System.out.println("Updated==>"+afterRemovingWhiteSpace);

or

String[] arr = {"467", "470", "464"};
List<String> idList = new LinkedList<>(Arrays.asList(arr));
System.out.println("==>"+idList);
String regex = "^\\s+";
idList.forEach(e -> e.replaceAll(regex, ""));
System.out.println("Updated==>"+idList);

But none works. Any idea how to do it efficiently, I don't want use array and remove an item from it, as list can contain large number of elements and that will become very costly operation.

This is not ArrayList it is LinkedList – janith1024 Jun 02 '20 at 05:22 — janith1024, Jun 02 '20 at 05:22

score 3 · Answer 1 · answered Jun 02 '20 at 05:20

3

Just use the contains method on the LinkedList

if (idList.contains(userId)) {

see https://docs.oracle.com/javase/7/docs/api/java/util/LinkedList.html#contains(java.lang.Object)

answered Jun 02 '20 at 05:20

Scary Wombat

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score 2 · Answer 2 · answered Jun 02 '20 at 05:20

2

Unless I'm missing something, instead of

if (idList.toString().contains(userId)) {

use List.contains(Object)

if (idList.contains(userId)) {

answered Jun 02 '20 at 05:20

Elliott Frisch

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List idList = new LinkedList<>(); idList.add("1"); idList.add(" 2"); String userId = "2"; if (idList.contains(userId)) { System.out.println("It Worked"); } – John Jun 02 '20 at 05:44
@Sam Why did you add a space when you added `2` to `idList`? `List idList = new LinkedList<>(Arrays.asList(arr));` does not do that. Also, if you only store `int` values, using a `List idList` would make more sense. Since `Integer` can never contain a space. – Elliott Frisch Jun 02 '20 at 05:46
I have string values and idList.add(" 2"), this is what I am getting after calling an API, cannot change it. – John Jun 02 '20 at 05:47
Then `trim()` the values. Or `trim()` and convert to `int`. And that's not a great result from calling an API. – Elliott Frisch Jun 02 '20 at 05:53
@Sam listen to Elliot. Otherwise `idList.add(" 123"); String userId = "12"; if (idList.toString().contains(userId)) { System.out.println("It failed"); } ` – daniu Jun 02 '20 at 06:03

matt · Answer 3 · 2020-06-02T06:32:20.717

You're printing out a list, the default toString will add spaces between elements.

System.out.println("[" + idList.stream().collect( Collectors.joining(",")) + "]");

That will concatenate the list without spaces.

This:

System.out.println("==>"+idList);

Adds spaces to the printed string only, not the elements of the list. So do both of these.

System.out.println("Updated==>"+afterRemovingWhiteSpace);
System.out.println("Updated==>"+idList);

The elements of the list were not changed

Another misconception you seem to be having.

"[123, 456]".contains("456");
"[123,456]".contains("456");

Both strings will contain 456, the spaces won't change that.

Also `"[123, 1456]".contains("456");` is also true – Scary Wombat Jun 02 '20 at 06:38 — Scary Wombat, Jun 02 '20 at 06:38

score 0 · Answer 4 · answered Jun 02 '20 at 06:18

0

You can trim spaces using this:

List<String> newList = new LinkedList<String>();
for(String x: idList)
        newList.add(x.trim());

answered Jun 02 '20 at 06:18

Harsh Somani

59
6

John · Accepted Answer · 2020-06-02T08:42:32.590

-2

This worked, by combining @matt answer's

List<String> idList = new LinkedList<>();
    idList.add("1");
    idList.add("          2");
    String userId = "2";
    List<String> removeLeadingWhiteSpacesList = new ArrayList<>();
    System.out.println("idList=>"+idList);
    for (String temp : idList) {
        removeLeadingWhiteSpacesList.add(temp.trim());
    }
    if (removeLeadingWhiteSpacesList.contains(userId)) {
        removeLeadingWhiteSpacesList.remove(userId);
        System.out.println("removeLeadingWhiteSpacesList=>"+removeLeadingWhiteSpacesList);
    }

It outputs

idList=>[1,           2]
removeLeadingWhiteSpacesList=>[1]

edited Jun 02 '20 at 08:42

answered Jun 02 '20 at 06:06

John

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As in my other comment, try `idList.add(" 123"); String userId = "12"; if (idList.stream().collect( Collectors.joining(",")).contains(userId)) { System.out.println("It failed"); } `. – daniu Jun 02 '20 at 06:24
Yup!, basically I have to trim the values and store it in other List and use that list. But this is what I did not wanted to do, as list is going to contain very large number of elements and it is not an optimized solution. Anyways Thanks for your efforts. – John Jun 02 '20 at 06:32
No, what you have to do is listen to the people here and check the list's content rather than analyzing a stringified version. – daniu Jun 02 '20 at 06:41

Arrays.asList(array) in java add unwanted spaces between comma separated string?

5 Answers5