Nam Ha Minh

Basically, this refers to the current instance (this instance) of the enclosing class. So whenever you need to access the current instance explicitly you need to use this.
Besides using this in setter methods, I also use it to call overloaded constructors, for example:

public class Customer {    private String name;    private String email;    public Customer(String name, String email) {        this.name = name;        this.email = email;    }    public Customer(String name) {        this(name, null);    } }

You can learn more about this keyword in Java here

Could you give some examples which Lambda expressions should be used on non-functional interfaces?

I think you use a collection (typically List) to store bikes rented by a customer.
Then returning a bike to the store is simply removing that bike from the collection.

Continue...
OrderDetail.java:

@Entity public class OrderDetail implements java.io.Serializable { private OrderDetailId id = new OrderDetailId(); private Book book; private BookOrder bookOrder; private int quantity; private float subtotal; public OrderDetail() { } @EmbeddedId @AttributeOverrides({ @AttributeOverride(name = "orderId", column = @Column(name = "order_id", nullable = false)), @AttributeOverride(name = "bookId", column = @Column(name = "book_id", nullable = false))}) public OrderDetailId getId() { return this.id; } public void setId(OrderDetailId id) { this.id = id; } @ManyToOne(fetch = FetchType.EAGER) @JoinColumn(name = "book_id", insertable = false, updatable = false, nullable = false) public Book getBook() { return this.book; } public void setBook(Book book) { this.book = book; this.id.setBook(book); } @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "order_id", insertable = false, updatable = false, nullable = false) public BookOrder getBookOrder() { return this.bookOrder; } public void setBookOrder(BookOrder bookOrder) { this.bookOrder = bookOrder; this.id.setBookOrder(bookOrder); } @Column(name = "quantity", nullable = false) public int getQuantity() { return this.quantity; } public void setQuantity(int quantity) { this.quantity = quantity; } @Column(name = "subtotal", nullable = false, precision = 12, scale = 0) public float getSubtotal() { return this.subtotal; } public void setSubtotal(float subtotal) { this.subtotal = subtotal; } }

OrderDetailId.java:

@Embeddable public class OrderDetailId implements java.io.Serializable { private Book book; private BookOrder bookOrder; public OrderDetailId() { } @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "book_id", insertable = false, updatable = false, nullable = false) public Book getBook() { return this.book; } public void setBook(Book book) { this.book = book; } @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "order_id", insertable = false, updatable = false, nullable = false) public BookOrder getBookOrder() { return this.bookOrder; } public void setBookOrder(BookOrder bookOrder) { this.bookOrder = bookOrder; } }

I hope this helps. I made that code based on these tutorials:

Hibernate Many-to-Many Association Annotations Example
Hibernate Many-to-Many Association with Extra Columns in Join Table Example

I did the same, and this is the working version on my side. For your reference (I remove unrelated code such as some unrelated fields, constructors, equals, hashcode... for the brevity):

Book.java:

@Entity @Table(name = "book", catalog = "bookstoredb", uniqueConstraints = @UniqueConstraint(columnNames = "title")) public class Book implements java.io.Serializable { private Integer bookId; private Category category; private String title; private String author; private Set<OrderDetail> orderDetails = new HashSet<OrderDetail>(0); public Book() { } @Id @GeneratedValue(strategy = IDENTITY) @Column(name = "book_id", unique = true, nullable = false) public Integer getBookId() { return this.bookId; } public void setBookId(Integer bookId) { this.bookId = bookId; } @ManyToOne(fetch = FetchType.EAGER) @JoinColumn(name = "category_id", nullable = false) public Category getCategory() { return this.category; } public void setCategory(Category category) { this.category = category; } @Column(name = "title", unique = true, nullable = false, length = 128) public String getTitle() { return this.title; } public void setTitle(String title) { this.title = title; } @Column(name = "author", nullable = false, length = 64) public String getAuthor() { return this.author; } public void setAuthor(String author) { this.author = author; } @OneToMany(fetch = FetchType.LAZY, mappedBy = "book") public Set<OrderDetail> getOrderDetails() { return this.orderDetails; } public void setOrderDetails(Set<OrderDetail> orderDetails) { this.orderDetails = orderDetails; } }

BookOrder.java:

@Entity public class BookOrder implements java.io.Serializable { private Integer orderId; private Set<OrderDetail> orderDetails = new HashSet<OrderDetail>(0); public BookOrder() { } @Id @GeneratedValue(strategy = IDENTITY) @Column(name = "order_id", unique = true, nullable = false) public Integer getOrderId() { return this.orderId; } public void setOrderId(Integer orderId) { this.orderId = orderId; } @OneToMany(fetch = FetchType.EAGER, mappedBy = "bookOrder", cascade = CascadeType.ALL, orphanRemoval = true) public Set<OrderDetail> getOrderDetails() { return this.orderDetails; } public void setOrderDetails(Set<OrderDetail> orderDetails) { this.orderDetails = orderDetails; } }

Hi, if you don't know where to start, I recommend you to read "Head First Java" - this is a really good book for beginners. Just by completing reading of this book, answer all its quizzes and do all its exercises  you will have a very good start in Java programming.

Ankit Minglani wrote:Hi All,

Happy to let you know that I have passed OCAJP8 - Programmer I - 1Z0-808 with 95% score. I have shared my preparation and experience for certification on my personal blog:

https://almostcurious.wordpress.com/2017/06/17/oracle-java-programmer-i-1z0-808-certification-with-95-score/

Would like to thank people in this community for keeping the culture of helping each other. It is really great for newcomers trying to take these certification exams or otherwise.

Thanks

CONGRATULATIONS! Great Score!

shambhavi ss wrote:alright thanks all , got it !      

i have another question !
class NoMoreCarrotsException extends Exception {} public class Bunny { public static void main(String[] args) throws NoMoreCarrotsException { eatCarrot(); } private static void eatCarrot() throws NoMoreCarrotsException { } }

in the above code, in line 3, if i do not declare the exception or if i do not handle it inside main(), i have a compiler error.

when the eatCarrot()  method has declared the exception then why should the main() again do it ?? if eatCarrot() method definition throws an exception, it'll be thrown as declared by its respective 'throws' clause in its signature, right ? why should we again declare the exception in main() i.e. in the caller of eatCarrot() ?

It's because when you call a method that throws an exception, the calling code must either handle it (by using try/catch structure), or re-throw it to the upper caller, i.e. throws in main() method in your case.

google "IBM UML class diagram". I remember IBM's website contains some quality articles about UML, which relate to their UML software Rational Rose

Welcome Chris Coyier. You're more than welcomed

Congratulations, you rock!
And thanks for the String notes.

Congratulations, you rock!
Can you tell me what books do you read?

Yeah, you should use SMTP settings of GMail instead.

Ok, thanks Jan.

Just look at Oracle site here:

https://education.oracle.com/pls/web_prod-plq-dad/ou_product_category.getPage?p_cat_id=266

There's no longer available of any courses or certifications for Java ME.

Does that mean Oracle discontinue it?