免费友情链接网站,湖州设计公司有哪些,制作网页网站公司,工作表格excel下载一.异常 1.概念 程序的非正常执行。高级语言都有异常处理机制#xff08;C#xff0c;Java#xff09; 2.一般处理异常的方法
Scanner sc new Scanner(System.in);System.out.println(请输入一个数字:);String s sc.nextLine();if (s.matches([0-9]CJava 2.一般处理异常的方法
Scanner sc new Scanner(System.in);System.out.println(请输入一个数字:);String s sc.nextLine();if (s.matches([0-9])) {int x Integer.parseInt(s);System.out.println(输入的数字是: x);
} else {System.out.println(程序异常);
}3.异常方式
Scanner sc new Scanner(System.in);System.out.println(请输入一个数字:);String s sc.nextLine();if (s.matches([0-9])) {int x Integer.parseInt(s);System.out.println(输入的数字是: x);
} else {System.out.println(程序异常);
}
4.异常机制
4.1 try 探测代码块是否有异常 try{语句块...
}
4.2 catch 异常捕获 cacth(异常对象 e){} 4.3 finally 有无异常一定执行。异常机制中 在Java中finally块通常用于释放资源、执行清理操作或记录错误。finally块总是会在try或catch块之后执行无论是否出现异常。如果try块中没有出现异常finally块将在try块之后立即执行如果try块中出现异常finally块将紧随catch块执行。 4.4 throws 方法上声明方法内有异常异常类型 4.5 throw 抛出异常对象 throw new 异常() public static void f() throws Exception{int a 1;int b 0;if(b0) throw new Exception(除0异常);
}5.异常体系 6.自定义异常
package com.ffyc.exception;public class MyException01 extends Exception{public MyException01(String msg){super(msg);}
}class MyException02 extends RuntimeException{public MyException02(String msg){super(msg);}
}class testMyException01{public static void test01() throws MyException01{throw new MyException01(自定义异常继承Exception);}public static void test02(){throw new MyException02(自定义异常继承RuntimeException);}public static void main(String[] args) {test02();try {test01();} catch (MyException01 e) {throw new RuntimeException(e);}}
}
7.图书系统
7.1借书 业务流程电脑查编号bookshell找书 package com.ffyc.service;import com.ffyc.entity.Book;//接口
public interface IBookService {Book borrowBook(String title);
}
package com.ffyc.exception;//实现
public class BookException extends RuntimeException{public BookException(String msg){super(msg);}
}
package com.ffyc.entity;import java.util.Date;public class Book {private String title;private String author;private String content;private String status;private Date borrowDate;private double price;public Book(){}public Book(String title, String author, String content, String status, Date borrowDate, double price) {this.title title;this.author author;this.content content;this.status status;this.borrowDate borrowDate;this.price price;}public String getTitle() {return title;}public void setTitle(String title) {this.title title;}public String getAuthor() {return author;}public void setAuthor(String author) {this.author author;}public String getContent() {return content;}public void setContent(String content) {this.content content;}public String getStatus() {return status;}public void setStatus(String status) {this.status status;}public Date getBorrowDate() {return borrowDate;}public void setBorrowDate(Date borrowDate) {this.borrowDate borrowDate;}public double getPrice() {return price;}public void setPrice(double price) {this.price price;}Overridepublic String toString() {return Book{ title title \ , author author \ , content content \ , status status \ , borrowDate borrowDate , price price };}
}
package com.ffyc.service.impl;import com.ffyc.entity.Book;
import com.ffyc.exception.BookException;
import com.ffyc.service.IBookService;import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;public class BookServiceImpl implements IBookService {private ListBook books new ArrayListBook();{books.add(new Book(西游记,武建军,我的大学生活,在库,null,33.44));}public Book borrowBook(String title) {IteratorBook it books.iterator();while (it.hasNext()){Book book it.next();if (book.getTitle().equals(title) book.getStatus().equals(在库)){return book;}}throw new BookException(图书已借出或丢失);}public static void main(String[] args) {IBookService ibs new BookServiceImpl();Book book ibs.borrowBook(西游记);System.out.println(book);}
}
