stream.findFirst() / anyMatch() / allMatch() / noneMatch()

// Returns the first element as an Optional.
stream.findFirst();

// Returns any element as an Optional (intended for parallel streams).
stream.findAny();

// Checks whether any element satisfies the condition.
stream.anyMatch(element -> condition);

// Checks whether all elements satisfy the condition.
stream.allMatch(element -> condition);

// Checks whether no elements satisfy the condition.
stream.noneMatch(element -> condition);

import java.util.Arrays;
import java.util.List;
import java.util.Optional;

List<String> names = Arrays.asList("Alice", "Bob", "Charlie", "David");

// Find the first name that starts with 'C'.
Optional<String> first = names.stream()
    .filter(name -> name.startsWith("C"))
    .findFirst();
System.out.println(first.orElse("Not found")); // Prints "Charlie".

// Check whether any name has 5 or more characters.
boolean hasLong = names.stream()
    .anyMatch(name -> name.length() >= 5);
System.out.println(hasLong); // Prints "true" (Alice, Charlie, David).

// Check whether all names have 3 or more characters.
boolean allLong = names.stream()
    .allMatch(name -> name.length() >= 3);
System.out.println(allLong); // Prints "true".

// Check whether no names contain digits.
boolean noDigit = names.stream()
    .noneMatch(name -> name.matches(".*\\d.*"));
System.out.println(noDigit); // Prints "true" (no names contain digits).

// Handle the case where findFirst returns an empty Optional.
Optional<String> empty = names.stream()
    .filter(name -> name.startsWith("Z"))
    .findFirst();
System.out.println(empty.isPresent()); // Prints "false".

Because findFirst() returns an Optional, you can handle the case where no element is found safely. Calling get() directly throws an exception if the element is absent, so use orElse() or isPresent() to retrieve the value safely.

anyMatch(), allMatch(), and noneMatch() use short-circuit evaluation. For example, anyMatch() stops evaluating the remaining elements as soon as it finds one that satisfies the condition, making it efficient.

For details on the Optional class, see Optional.of() / isPresent() / orElse().