在本教程中，我们将看到如何在Java中创建自定义异常。
在Java中创建自定义异常非常简单。
我们只需要扩展异常类以创建自定义异常。

我们有country的名单，如果我们在国家/地区中有"USA"，则需要抛出InvalidCountryException(我们的自定义异常)。

示例：创建InvalidCountryException.java，如下所示

package org.igi.theitroad;
 
public class InvalidCountryException extends Exception{
 
 InvalidCountryException(String message)
 {
  super(message);
 }
}

创建叫做Country.java的Pojo类

package org.igi.theitroad;
 
public class Country {
 
 private String name;
 
 Country(String name ){
 this.name = name;
 }
  public String toString() {
   return name;
  }
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name;
 }
  
 
}

让我们创建CountryCheckmain.java。
此类将具有主要方法。

package org.igi.theitroad;
 
import java.util.ArrayList;
import java.util.List;
 
public class CountryCheckMain {
 
 public static void main(String args[]) {
  List countries = new ArrayList();
  Country NetherlandsCountry = new Country("Netherlands");
  Country chinaCountry = new Country("China");
  Country nepalCountry = new Country("Nepal");
  Country bhutanCountry = new Country("Bhutan");
  countries.add(NetherlandsCountry);
  countries.add(chinaCountry);
  countries.add(nepalCountry);
  countries.add(bhutanCountry);
  boolean safe;
  try {
   safe = checkListOfCountries(countries);
   if (safe)
    System.out.println("We don't have USA in list of Countries");
   Country USACountry = new Country("USA");
   countries.add(USACountry);
   checkListOfCountries(countries);
  } catch (InvalidCountryException e) {
   e.printStackTrace();
  }
 
 }
 
 public static boolean checkListOfCountries(List countries) throws InvalidCountryException {
  for (int i = 0; i < countries.size(); i++) {
   Country country = countries.get(i);
   if (country.getName().equals("USA")) {
    throw new InvalidCountryException("USA is not allowed");
   }  
  }
  return true;
 }
}

运行上面的程序时，我们将获取以下输出：

We don't have USA in list of Country
org.igi.theitroad.comvalidCountryException: USA is not allowed
 at org.igi.theitroad.CountryCheckMain.checkListOfCountries(CountryCheckMain.java:37)
 at org.igi.theitroad.CountryCheckMain.main(CountryCheckMain.java:25)

正如我们所看到的，如果我们在国家名单中有"美国"，我们正在抛出InvalidCountryException。