Delete 'Java面向对象 - Java中的异常.txt'

master
pj3q7x5mz 2 years ago
parent f188f29ded
commit c3158d0c32

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1.Java 中的异常处理机制
编译出错提示“公有类HelloWorld必须在HelloWorld.java文件中定义”
IOException及其子类FileNotFoundException等都属于检测型异常运行时异常可以处理也可以不处理是可选的
所有的异常类是从 java.lang.Exception 类继承的子类)
运行时报错提示除数不能为0
2.捕获异常
package step2;
import java.util.Scanner;
public class Task {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int num1 = sc.nextInt();
int num2 = sc.nextInt();
/********* Begin *********/
try{
System.out.println(num1/num2);}
catch(ArithmeticException e){
System.out.print("除数不能为0");
}
/********* End *********/
}
}
3.抛出异常
package step3;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
public class Task {
public static void main(String[] args)throws FileNotFoundException{
test();
}
public static void test()throws FileNotFoundException{
File file = new File("abc");
if(!file.exists()){ //判断文件是否存在
//文件不存在,则 抛出 文件不存在异常
throw new FileNotFoundException("该文件不存在");
}else{
FileInputStream fs = new FileInputStream(file);
}
}
/********* End *********/
}
4.自定义异常
package step4;
import java.util.Scanner;
public class Task {
/********* Begin *********/
public static void main(String[] args)throws MyException {
Scanner sc = new Scanner(System.in);
String username = sc.next();
//判断用户名
if(username.length()<3){
throw new MyException("用户名小于三位Exception");
}
else{
System.out.println("用户名格式正确");
}
}
}
class MyException extends Exception{
public MyException(){}
public MyException(String msg){
super(msg);
}
}
/********* End *********/
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