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How to check if element exists using a lambda expression?

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Can we use if condition in lambda expression Java?

The 'if-else' condition can be applied as a lambda expression in forEach() function in form of a Consumer action.

How do you read a lambda expression?

All lambda expressions use the lambda operator =>, which is read as "goes to". The left side of the lambda operator specifies the input parameters (if any) and the right side hold the expression or statement block. The lambda expression x => x * 2 is read "x goes to 2 times x." This reduced the no.

Can we use this in lambda expression?

The "this" and "super" references within a lambda expression are the same as in the enclosing context. Since the lambda expression doesn't define a new scope, "this" keyword within a lambda expression signifies "this" parameter of a method where the lambda expression is residing.


Try to use anyMatch of Lambda Expression. It is much better approach.

 boolean idExists = tabPane.getTabs().stream()
            .anyMatch(t -> t.getId().equals(idToCheck));

While the accepted answer is correct, I'll add a more elegant version (in my opinion):

boolean idExists = tabPane.getTabs().stream()
    .map(Tab::getId)
    .anyMatch(idToCheck::equals);

Don't neglect using Stream#map() which allows to flatten the data structure before applying the Predicate.


The above answers require you to malloc a new stream object.

public <T>
boolean containsByLambda(Collection<? extends T> c, Predicate<? super T> p) {

    for (final T z : c) {
        if (p.test(z)) {
            return true;
        }
    }
    return false;
}

public boolean containsTabById(TabPane tabPane, String id) {
    return containsByLambda(tabPane.getTabs(), z -> z.getId().equals(id));
}
...
if (containsTabById(tabPane, idToCheck))) {
   ...
}