What is the way to define custom exceptions in Java?

1. What types of exceptions are there?

Exceptions are divided into two types, namely compilation exceptions and runtime exceptions.

Compile-time exceptions

• are all Exception classes and their subclasses

• must be handled explicitly , otherwise an error will occur in the program and cannot be compiled

##Runtime exceptions

• are all RuntimeException classes and their Subclasses

• No need to display the processing, and can also be processed in the same way as compile-time exceptions

package com.xxgc.chop5_2.test;
 
public class ExceptionDemo {
    public static void show4(){
        //把字符串转换int类型
        String a="张三";
        int b=Integer.parseInt(a);//NumberF
    }
    //异常抛出
    public static void show3() throws ClassNotFoundException {
        Class.forName("Student");
    }
    public static void show2(){
        //运行时异常：程序运行的时候出现的异常，可以try
        //编译时异常（非运行时异常）：必须try catch 或者向上抛出
        try {
            Class.forName("Student");
        }catch (ClassNotFoundException e){
            e.printStackTrace();
        }
    }
    public static void show() {
        //制造一个异常，捕获异常，处理异常
        try{
           int []nums={1,2};
           int n=10/0;
           int a=nums[3];
        }catch (ArrayIndexOutOfBoundsException e) {
            e.printStackTrace();
            System.out.println("数组下标出错了");
        }catch (Exception e){
            e.printStackTrace();
            System.out.println("出错了");
        }finally {
            //最终最后都要之心的代码，一般完成资源释放工作
            System.out.println("最终的！！！");
        }
    }
 
    public static void main(String[] args) {
        //trows：向上抛出异常，抛给方法的调用者
        //show3（）方法向上抛出了异常，需要main方法解决
        //1.main方法解决了
        //2.main没解决完，继续向上抛，jvm(Java虚拟机)解决
        try {
            show3();
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }
    }
}

2. Custom exceptions

1. First create a new class

This class is a custom exception class. First we inherit the RuntimeException of idea, and then create methods with and without parameters.

The code is as follows (example):

package com.xxgc.ch06.po;
 
public class MyException extends RuntimeException{
    public MyException(){
 
    }
    public MyException(String s){
        super(s);
    }
 
}

2. Test class

Create a new test class below, with main method and shou method. Define an int type a in the shou method, and enter if to determine whether a is abnormal.

The code is as follows (example):

package com.xxgc.ch06.test;
 
import com.xxgc.ch06.po.MyException;
 
public class ThrowDemo {
    public static void show(){
        //如果a>10，抛出自己的异常
        int a=13;
        if (a>10){
            try {
                throw new MyException("不能大于10");
            }catch (MyException e){
                e.printStackTrace();
                System.out.println("出错啦！"+e.getMessage());
            }
 
 
        }
        System.out.println("扶苏");
    }
 
    public static void main(String[] args) {
        show();
    }
}

The idea software used here.

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