What’s the best way to check if a list contains an item other than specified item?-CodePudding

I have a list and I want to know if there exist elements in it that are not a particular value.

List<String> items = new ArrayList<>():

How do it return false if items contains an element other than some String, say "apple"?

CodePudding user response：

With Stream IPA you can achieve that by using terminal operation allMath() that takes a predicate (function represented by boolean condition) and checks whether all elements in the stream match with the given predicate.

The code will look like that:

public static void main(String[] args) {
    List<String> items1 = List.of("apple", "apple", "apple"); // expected true
    List<String> items2 = List.of("apple", "orange"); // expected false

    System.out.println(items1.stream().allMatch(item -> item.equals("apple")));
    System.out.println(items2.stream().allMatch(item -> item.equals("apple")));
}

output

true
false

CodePudding user response：

I use python but, I think is something like that:

list_entrance = input()

new_list = []

for cycle in list_entrance: if cycle != "apple": print("falce") else: continue

If you want of course you can "append" a items in "new_list". I don't know full condition on your task.

CodePudding user response：

Just to say your ArrayList should be defined like this:

List items = new ArrayList<>();

You missed out some caps in the question.

For the solution you could just loop through the list and check:

for (int x = 0; x<items.size(); x  ){
    if (! items.get(x).equals("apple")){
        return false;
    } 
}
return true;

CodePudding user response：

Here's a one-liner:

return items.stream().anyMatch(s -> !s.equals("apple"));

or cute but a little less obvious:

return items.stream().allMatch("apple"::equals);

CodePudding user response：

Instead use a Set, in order not to have duplicate items.

Collectors can also return Set:

Set<String> distinct = list.stream().collect(Collectors.toSet());