After learning the knowledge of object-oriented programming syntax and simple data structure sequence table, we can now use these knowledge to comprehensively implement a library management system to test the mastery of the previous knowledge and practice the actual coding ability of the code, so as to further understand Java development. We don't say much and begin to explain~
1. Implementation of book package
First, we implement a book package, in which a Book class is defined respectively to realize the definition and operation of books; And a BookList class, equivalent to a bookshelf, used to store books. In essence, it is a sequential table in a data structure to find and modify specific books.
//Relevant explanations are given in the form of comments in the code. Please pay attention to them
1.1 Book class
package book;
public class Book {
private String name; //title
private String author;//author
private int price;//book prices
private String type;//Types of books
private boolean isBorrowed;//Is the status of the book lent
//Rewrite construction method is used to define a book
public Book(String name, String author, int price, String type) {
this.name = name;
this.author = author;
this.price = price;
this.type = type;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
public int getPrice() {
return price;
}
public void setPrice(int price) {
this.price = price;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public boolean isBorrowed() {
return isBorrowed;
}
public void setBorrowed(boolean borrowed) {
isBorrowed = borrowed;
}
//Override the toString method to print the book information
@Override
public String toString() {
return "Book{" +
"name='" + name + '\'' +
", author='" + author + '\'' +
", price=" + price +
", type='" + type + '\'' + " "+
((isBorrowed==true)?"Has been lent out":"Not lent")+
'}';
}
}
1.2 BookList class
package book;
public class BookList {
private Book[] books=new Book[10]; //Define an array of Book type and initialize the space for 10 books
private int usedSize;//Number of books currently in storage
public BookList(){
books[0]=new Book("Romance of the Three Kingdoms","Luo Guanzhong",17,"novel");
books[1]=new Book("Journey to the West","Wu Chengen",47,"novel");
books[2]=new Book("Water Margin","Shi Naian",37,"novel"); //Give three books for practice
this.usedSize=3;
}
public int getUsedSize() {
return usedSize;
}
public void setUsedSize(int usedSize) {
this.usedSize = usedSize;
}
/**
* Get a book at pos
* @param pos
* @return
*/
public Book getPos(int pos){
return this.books[pos];
}
/**
* Set the subscript of pos position as a Book (add a Book)
* @param pos
* @param book
*/
public void setBook(int pos,Book book){
this.books[pos]=book;
}
}
2.operation package
Because object-oriented programming practice is required, an operation package is implemented separately to realize various operations on books. The original code of this part can be placed in the sequence table of BookList, but the operation package can have a clearer understanding of object-oriented programming~
2.1 IOperation interface
package operation;
import book.BookList;
import java.util.Scanner;
public interface IOperation {
void work(BookList bookList);
//The keyboard input data code can be directly implemented in the interface without writing the necessary code in each class
Scanner scanner=new Scanner(System.in);
}
2.2 AddOperation class
This class implements the function of adding books
package operation;
import book.Book;
import book.BookList;
import java.util.Scanner;
public class AddOperation implements IOperation { //Implementation interface
public void work(BookList bookList) { //Method of rewriting interface
System.out.println("New books!");
System.out.println("Please enter the name of the book to be added:");
String name = scanner.nextLine();
System.out.println("Author:");
String author = scanner.nextLine();
System.out.println("Type:");
String type = scanner.nextLine();
System.out.println("Price:");
int price = scanner.nextInt();
Book book = new Book(name, author, price, type);//Construct a book that needs to be added
int size = bookList.getUsedSize();
bookList.setBook(size, book);
bookList.setUsedSize(size + 1);
System.out.println("Successfully added books!");
}
}
2.2 BorrowOperation class
Book borrowing function
package operation;
import book.Book;
import book.BookList;
public class BorrowOperation implements IOperation{
public void work(BookList bookList){
System.out.println("Borrow books!");
System.out.println("Please enter the name of the book you want to borrow:");
String name=scanner.nextLine();
int size=bookList.getUsedSize();
for (int i = 0; i < size; i++) {
Book book=bookList.getPos(i);
if (name.equals(book.getName())){
book.setBorrowed(true);
System.out.println("Borrowing succeeded!");
System.out.println(book);
return;
}
}
System.out.println("I can't find the book you want to borrow!");
}
}
2.3 ReturnOperation class
Return book function
package operation;
import book.Book;
import book.BookList;
public class ReturnOperation implements IOperation{
public void work(BookList bookList){
System.out.println("Return the books!");
System.out.println("Please enter the name of the book you want to return:");
String name=scanner.nextLine();
int size=bookList.getUsedSize();
for (int i = 0; i < size; i++) {
Book book=bookList.getPos(i);
if (name.equals(book.getName())){
book.setBorrowed(false);
System.out.println("Return succeeded!");
System.out.println(book);
return;
}
}
System.out.println("I haven't found the book you want to return!");
}
}
2.4 DelOperation class
Delete specified book function
package operation;
import book.Book;
import book.BookList;
public class DelOperation implements IOperation{
public void work(BookList bookList){
System.out.println("Delete books!");
//1. Find the location of the book according to the book title
System.out.println("Please enter the title of the book you want to delete:");
String name=scanner.nextLine();
int currentSize=bookList.getUsedSize();
int index=0; //Store the subscript of the book to be deleted
int i = 0;
for (; i < currentSize; i++) {
Book book=bookList.getPos(i);
if (book.getName().equals(name)){
index=i;
break;
}
}
if (i>=currentSize){
System.out.println("There is no book you want to delete!");
return;
}
//2. Delete!
for (int j = index; j < currentSize-1; j++) { //The reason why it is less than currentSize-1 is to avoid the array out of bounds and error reporting. The deletion operation only needs to find the currentSize-1 subscript
Book book=bookList.getPos(j+1);
bookList.setBook(j,book); //The operation idea is to give the j+1 subscript content to j to realize the deletion effect
}
bookList.setBook(currentSize,null); //Don't forget to empty the last subscript
bookList.setUsedSize(currentSize-1);//The number of books is reduced by one
System.out.println("Delete succeeded!");
}
}
2.5 DisplayOperation class
Print the current bookshelf information
package operation;
import book.Book;
import book.BookList;
public class DisplayOperation implements IOperation{
public void work(BookList bookList){
System.out.println("Print books!");
int size=bookList.getUsedSize();
for (int i = 0; i < size; i++) {
Book book=bookList.getPos(i);
System.out.println(book);
}
}
}
2.6 FindOperation class
Realize the function of finding specified books and printing book information
package operation;
import book.Book;
import book.BookList;
public class FindOperation implements IOperation{
public void work(BookList bookList){
System.out.println("Find books!");
String name=scanner.nextLine();
int size=bookList.getUsedSize();
for (int i = 0; i < size; i++) {
Book book=bookList.getPos(i);
if (name.equals(book.getName())){
System.out.println("Found the book,The information is as follows:");
System.out.println(book);
return;
}
}
System.out.println("I didn't find the book!");
}
}
2.7 ExitOperation class
Realize the function of exiting the library management system
package operation;
import book.BookList;
public class ExitOperation implements IOperation{
public void work(BookList bookList){
System.out.println("Exit the system!");
System.exit(0); //0 indicates normal exit
}
}
3.user package
Because different functions need to be implemented for different users, the user package here implements the functions required by administrators and ordinary users respectively
3.1 User class (parent class)
package user;
import book.BookList;
import operation.IOperation;
public abstract class User { //Abstract class implementation
protected String name; //User name
protected IOperation[] iOperations;//Interface array implementation
public User(String name){ //Override User constructor
this.name=name;
}
public abstract int menu(); //Different user menus are implemented for different user input options
//Select and implement different operation operations according to user input
public void doWork(int choice, BookList bookList){
iOperations[choice].work(bookList);
}
}
3.2 AdminUser administrator class (subclass)
package user;
import operation.*;
import java.util.Scanner;
public class AdminUser extends User{
public AdminUser(String name){ //Subclass construction method
super(name); //Override parent class constructor
this.iOperations=new IOperation[] { //!! Administrator function implementation!!
new ExitOperation(),
new FindOperation(),
new AddOperation(),
new DelOperation(),
new DisplayOperation(),
};
}
public int menu(){
System.out.println("==========Administrator menu==========");
System.out.println("hello"+this.name+"Welcome to this system!");
System.out.println("1.Find books");
System.out.println("2.New books");
System.out.println("3.Delete book");
System.out.println("4.Show books");
System.out.println("0.Exit the system");
System.out.println("============================");
Scanner scanner=new Scanner(System.in);
int choice=scanner.nextInt();
return choice;
}
}
3.3 NormalUser general user class (subclass)
package user;
import operation.*;
import java.util.Scanner;
public class NormalUser extends User{
public NormalUser(String name) { //Override subclass constructor
super(name);//Override parent class constructor
this.iOperations=new IOperation[] {
new ExitOperation(),
new FindOperation(),
new BorrowOperation(),
new ReturnOperation(),
};
}
public int menu(){
System.out.println("==========General user menu==========");
System.out.println("hello"+this.name+"Welcome to this system!");
System.out.println("1.Find books");
System.out.println("2.Borrow books");
System.out.println("3.Return books");
System.out.println("0.Exit the system");
System.out.println("============================");
Scanner scanner=new Scanner(System.in);
int choice=scanner.nextInt();
return choice;
}
}
4. Program entry Main class implementation
import book.BookList;
import user.AdminUser;
import user.NormalUser;
import user.User;
import java.util.Scanner;
/**
* The entrance of the whole program
*/
public class Main {
public static User login(){
System.out.println("Please enter your name:");
Scanner scanner=new Scanner(System.in);
String name=scanner.nextLine();
System.out.println("Please enter your identity: 1->administrators. 0->Ordinary users");
int choice=scanner.nextInt();
if (choice==1){ //Implement different user classes according to user selection
return new AdminUser(name);
}else{
return new NormalUser(name);
}
}
public static void main(String[] args) {
BookList bookList=new BookList();
User user=login(); //Upward Transformation: parent class reference (user) refers to subclass object (AdminUser(name)/NormalUser(name))
while(true) { //If you exit the system without manual input, the system will continue to cycle
int choice = user.menu();//A dynamic binding (runtime binding) has occurred
//Call the appropriate operation according to choice
user.doWork(choice, bookList);
}
}
}
5. Overall code implementation display
After realizing the above four blocks of code, and the Main class connects the functions of each module through upward transformation, our simple library management system has been completed! This is a good exercise project to practice all the knowledge since Java learning. It is worth learning and practicing code repeatedly~
The overall code implementation is shown as follows:
5.1 display of administrator function realization (part)
5.2 ordinary user function realization display (part)
6 end
Here, a simple library management system has been completed~
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