First of all, I recommend this article: Java: When to create a final class If they do, when do they use it so I can understand it better and know when to use it. A final class is simply a class that can’t be extended. (It does not mean that all references to objects of … Read more
For IntelliJ 13, there is a checkbox in Editor’s page in IDE Settings EDIT: For IntelliJ 14, the option has been moved to Editor > General page. It’s the last option in the “Other” group. (For Mac the option is under the menu “IntelliJ Idea” > “Preferences”). EDIT: For IntelliJ 16, it’s the second-to-last option … Read more
You can find an overview of a lot of design patterns in Wikipedia. It also mentions which patterns are mentioned by GoF. I’ll sum them up here and try to assign as many pattern implementations as possible, found in both the Java SE and Java EE APIs. Creational patterns Abstract factory (recognizeable by creational methods … Read more
The three forms of looping are nearly identical. The enhanced for loop: for (E element : list) { . . . } is, according to the Java Language Specification, identical in effect to the explicit use of an iterator with a traditional for loop. In the third case, you can only modify the list contents … Read more
You could define callFriend this way: public <T extends Animal> T callFriend(String name, Class<T> type) { return type.cast(friends.get(name)); } Then call it as such: jerry.callFriend(“spike”, Dog.class).bark(); jerry.callFriend(“quacker”, Duck.class).quack(); This code has the benefit of not generating any compiler warnings. Of course this is really just an updated version of casting from the pre-generic days and … Read more
The obvious answer, of course, is not to do the unchecked cast. If it’s absolutely necessary, then at least try to limit the scope of the @SuppressWarnings annotation. According to its Javadocs, it can go on local variables; this way, it doesn’t even affect the entire method. Example: @SuppressWarnings(“unchecked”) Map<String, String> myMap = (Map<String, String>) … Read more
@Mock creates a mock. @InjectMocks creates an instance of the class and injects the mocks that are created with the @Mock (or @Spy) annotations into this instance. Note you must use @RunWith(MockitoJUnitRunner.class) or Mockito.initMocks(this) to initialize these mocks and inject them (JUnit 4). With JUnit 5, you must use @ExtendWith(MockitoExtension.class). @RunWith(MockitoJUnitRunner.class) // JUnit 4 // … Read more
As you state JPA is just a specification, meaning there is no implementation. You can annotate your classes as much as you would like with JPA annotations, however without an implementation nothing will happen. Think of JPA as the guidelines that must be followed or an interface, while Hibernate’s JPA implementation is code that meets … Read more
Sometimes you have two entities and there’s a relationship between them. For example, you might have an entity called University and another entity called Student and a University might have many Students: The University entity might have some basic properties such as id, name, address, etc. as well as a collection property called students that … Read more
Assertions (by way of the assert keyword) were added in Java 1.4. They are used to verify the correctness of an invariant in the code. They should never be triggered in production code, and are indicative of a bug or misuse of a code path. They can be activated at run-time by way of the … Read more