5.5. Optional. Методы orElseThrow()

src/main/java/ru/job4j/lambda/OptionalOrElseThrow.java

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+package ru.job4j.lambda;
+
+import java.util.List;
+import java.util.Optional;
+
+public class OptionalOrElseThrow {
+
+    public record User(String login) {
+    }
+
+    public static class UserNotFoundException extends RuntimeException {
+    }
+
+    public static User orElseThrow(List<User> list, String login) {
+        return search(list, login).orElseThrow(UserNotFoundException::new);
+    }
+
+    private static Optional<User> search(List<User> list, String login) {
+        Optional<User> result = Optional.empty();
+        for (User user : list) {
+            if (user.login().equals(login)) {
+                result = Optional.of(user);
+            }
+        }
+        return result;
+    }
+}

src/test/java/ru/job4j/lambda/OptionalOrElseThrowTest.java

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+package ru.job4j.lambda;
+
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static ru.job4j.lambda.OptionalOrElseThrow.User;
+import static ru.job4j.lambda.OptionalOrElseThrow.UserNotFoundException;
+
+public class OptionalOrElseThrowTest {
+
+    @Test
+    public void whenFound() {
+        User u1 = new User("u1");
+        User u2 = new User("u2");
+        User u3 = new User("u3");
+        assertEquals(u3.login(), OptionalOrElseThrow.orElseThrow(
+                List.of(u1, u2, u3), u3.login()).login());
+    }
+
+    @Test(expected = UserNotFoundException.class)
+    public void whenNotFound() {
+        User u1 = new User("u1");
+        User u2 = new User("u2");
+        User u3 = new User("u3");
+        OptionalOrElseThrow.orElseThrow(List.of(u1, u2, u3), "u4");
+    }
+}