Class design
- Java course
- Intermediate
- Lesson 19/116
- 6 min
Design the library class skeleton.
Project: Library system
In this 5-lesson project you'll build a library system. Each lesson adds one piece, and by the final lesson you'll have a working program.
You'll use what you learned in previous groups: classes, constructors and inheritance. Throughout the project you'll define Library, Book, Member and Loan classes. In the first lesson you'll create the skeleton of the Library class: a name field, a constructor and a toString method.
The Library class skeleton
The first lesson defines the Library class. The class will have a name field, a constructor and a toString method. The constructor takes the name as a parameter and assigns it to the field.
Example skeleton: class Library { String name; Library(String n) { name = n; } public String toString() { return "Library: " + name; } }. This class forms the foundation for later lessons. Each lesson adds a new class on top. The constructor and toString provide a standard structure; book and member lists will be added later.
Practice Define the Library class
Define a class named Library. Add a String name field. Write a Library(String n) constructor that assigns name = n;. Add a public String toString() method returning "Library: " + name. In main create a Library instance and print it with println.
Starter code
// Define the Library class
// Add field, constructor and toString
// Instantiate and print in mainSample solution
class Library {
String name;
Library(String n) {
name = n;
}
public String toString() {
return "Library: " + name;
}
public static void main(String[] args) {
Library lib = new Library("Central");
System.out.println(lib);
}
}Expected output
Library: Central
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which class is defined in the first lesson of the library system?
- Library Correct answer
- Book
- Member
- Loan
Explanation: The first lesson creates the skeleton of the Library class.
2 Complete the Library constructor
class Library {
String name;
____(String n) {
name = n;
}
}class Library {
String name;
Library(String n) {
name = n;
}
}Explanation: The constructor name must match the class name.
3 Match the Library parts
| Term | Meaning |
|---|---|
String name |
Field |
Library(String n) |
Constructor |
toString |
String method |
new Library(...) |
Instantiation |