Throws Keyword in Java

Throws Keyword

As we know that there are two types of exception – checked and unchecked. Checked exceptions (compile time) are the one which forces the programmer to handle it, without which the program doesn’t compile successfully. While unchecked exception (Runtime) doesn’t get checked during compilation. “Throws keyword” is mainly used for handling checked exception as using throws we can declare multiple exceptions in one go. Let’s understand this with the help of an example.

Example of throws Keyword

In this example the method “mymethod” is throwing two checked exceptions so we have declared those exceptions in the method signature using throws Keyword. If we do not declare these exceptions then the program will throw a compilation error.

import java.io.*;
public class ThrowExample { 
  void mymethod(int num)throws IOException, ClassNotFoundException{ 
     if(num==1)
        throw new IOException("Exception Message1");
     else
        throw new ClassNotFoundException("Exception Message2");
  } 
} 

class Demo{ 
  public static void main(String args[]){ 
   try{ 
     ThrowExample obj=new ThrowExample(); 
     obj.mymethod(1); 
   }catch(Exception ex){
     System.out.println(ex);
    } 
  }
}

Output :

java.io.IOException: Exception Message1

Since we passed the argument as 1 during the function call, the program thrown IOException.