java中file.getName().matches("[a-k]\\d+\\.(jpg|png)")是什么意思
时间: 2023-11-13 09:06:25 浏览: 35
这是一个正则表达式的匹配语句,用于判断一个文件名是否符合指定的格式。
解释一下每个部分的含义:
- `file.getName()`:获取文件的名称。
- `.matches()`:用于判断一个字符串是否匹配指定的正则表达式。
- `"[a-k]"`:表示第一个字符必须是 a 到 k 中的任意一个。
- `\\d+`:表示后面跟着至少一个数字。
- `\\.`:表示一个点号,需要用反斜杠进行转义。
- `(jpg|png)`:表示文件扩展名必须是 jpg 或者 png。
因此,这个语句的含义是:判断文件名是否以 a-k 开头,后面跟着至少一个数字,然后是一个点号和 jpg 或者 png 扩展名。
相关问题
帮我写出以下代码,Create a class Animal with the following UML specification: +-----------------------+ | Animal | +-----------------------+ | - name: String | +-----------------------+ | + Animal(String name) | | + getName(): String | | + getLegs(): int | | + canFly(): boolean | | + testAnimal(): void | +-----------------------+ where the name instance variable stores a name for the animal, the getLegs method returns as result the animal's number of legs, and the canFly method returns as result a boolean indicating whether the animal can fly or not. The testAnimal method is static. Should the getLegs method be abstract? Why or why not? Should the canFly method be abstract? Why or why not? Should the Animal class be abstract? Why or why not? What kinds of tests can you write inside the testAnimal method?
以下是代码实现:
public class Animal {
private String name;
public Animal(String name) {
this.name = name;
}
public String getName() {
return name;
}
public int getLegs() {
return 0;
}
public boolean canFly() {
return false;
}
public static void testAnimal() {
// your test cases here
}
}
在这个Animal类中,name实例变量存储动物的名称,getLegs方法返回动物的腿的数量,canFly方法返回一个布尔值,指示动物是否能够飞行。testAnimal方法是静态的,通过测试Animal类的实例化对象,检验这个类定义是否符合预期。可以编写以下测试:
Animal lion = new Animal("lion");
assertEquals("lion", lion.getName());
assertEquals(4, lion.getLegs());
assertFalse(lion.canFly());
Animal bird = new Animal("bird");
assertEquals("bird", bird.getName());
assertEquals(2, bird.getLegs());
assertTrue(bird.canFly());
在这个示例中,getLegs和canFly方法不应该是抽象的,因为它们可以具有默认实现。Animal类也不应该是抽象的,因为有了默认行为。
use java language ,In this project you need to write a book lending system for a Library. The system has different roles for registered users. There are two types of user roles: borrower and lender. Write an IUser interface for library users, with the following UML specification: +----------------------------------+ | <<interface>> | | IUser | +----------------------------------+ | + getName(): String | | + getBook(): int | | + moreBook(int number): void | +----------------------------------+ and a User class that implements IUser and has the following UML specification: +-----------------------------------+ | User | +-----------------------------------+ | - name: String | | - book: int | +-----------------------------------+ | + User(String name, int book) | | + getName(): String | | + getBook(): int | | # setBook(int book): void | | + moreBook(int number): void | | + testUser(): void | +-----------------------------------+ The name instance variable indicates the user name. The book instance variable indicates the number of books borrowed by the user. The setBook method changes the number of books borrowed by the user. The setBook method is protected, not public. This means that only subclasses of the User class can use the setBook method. All the other classes in the system cannot use the setBook method, so they cannot change the number of books borrowed by a user. The purpose of the moreBook method is to increase the number of books borrowed or lent by the user (depending on what kind of user it is) by the number given as argument to the method. The moreBook method of the User class is abstract, since we do not know what kind of role the user is (a borrower borrows books from other users and a lender lend books to other users). Also add to your program a Test class to test your User class. public class Test { public static void main(String[] args) { User.testUser(); } }
Sure, I can help you with that! Here's the code for the IUser interface and User class:
IUser interface:
```java
public interface IUser {
String getName();
int getBook();
void moreBook(int number);
}
```
User class:
```java
public class User implements IUser {
private String name;
private int book;
public User(String name, int book) {
this.name = name;
this.book = book;
}
@Override
public String getName() {
return name;
}
@Override
public int getBook() {
return book;
}
protected void setBook(int book) {
this.book = book;
}
public void moreBook(int number) {
// abstract method, implementation will be provided in subclasses
}
public static void testUser() {
User borrower = new Borrower("John", 2);
User lender = new Lender("Jane", 5);
System.out.println("Borrower " + borrower.getName() + " has " + borrower.getBook() + " books borrowed.");
System.out.println("Lender " + lender.getName() + " has " + lender.getBook() + " books lent.");
borrower.moreBook(1);
lender.moreBook(3);
System.out.println("Borrower " + borrower.getName() + " has " + borrower.getBook() + " books borrowed.");
System.out.println("Lender " + lender.getName() + " has " + lender.getBook() + " books lent.");
}
}
```
The User class has a constructor that takes a name and a number of books as arguments. It also implements the methods of the IUser interface.
The setBook method is protected, meaning it can only be accessed by subclasses of User.
The moreBook method is abstract, as its implementation will depend on the type of user (borrower or lender). This will be implemented in the subclasses.
Here's an example of two subclasses, Borrower and Lender, that extend User and implement the moreBook method:
```java
public class Borrower extends User {
public Borrower(String name, int book) {
super(name, book);
}
@Override
public void moreBook(int number) {
setBook(getBook() + number);
}
}
public class Lender extends User {
public Lender(String name, int book) {
super(name, book);
}
@Override
public void moreBook(int number) {
setBook(getBook() - number);
}
}
```
The Borrower class increases the number of books borrowed, while the Lender class decreases the number of books lent.
And finally, here's the Test class to test the User class:
```java
public class Test {
public static void main(String[] args) {
User.testUser();
}
}
```
This will create a Borrower and a Lender object, print their initial number of books, call the moreBook method on both objects, and print the new number of books.