Lets understand this with example. You have list of counties and if You have “USA” in list of country, then you need to throw invalidCountryException(Our custom exception).
Example:
Create InvalidCountryException.java as below
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package org.arpit.java2blog; public class InvalidCountryException extends Exception{ InvalidCountryException(String message) { super(message); } } |
Create POJO class called Country.java
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package org.arpit.java2blog; 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; } } |
Lets create CountryCheckMain.java. This class will have main method.
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package org.arpit.java2blog; import java.util.ArrayList; import java.util.List; public class CountryCheckMain { public static void main(String args[]) { List countries = new ArrayList(); Country indiaCountry = new Country("India"); Country chinaCountry = new Country("China"); Country nepalCountry = new Country("Nepal"); Country bhutanCountry = new Country("Bhutan"); countries.add(indiaCountry); 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; } } |
When you run above program, you will get following output:
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We don't have USA in list of Country org.arpit.java2blog.InvalidCountryException: USA is not allowed at org.arpit.java2blog.CountryCheckMain.checkListOfCountries(CountryCheckMain.java:37) at org.arpit.java2blog.CountryCheckMain.main(CountryCheckMain.java:25) |
As you can see, if we have “USA” in list of Countries,we are throwing InvalidCountryException.