Java Tutorial 25 – “throws” keyword

In your program you will handle this exception using try & catch.

import java.io.*;
class file1{
  public static void main(String[] args) {
     try{
           FileWriter file = new FileWriter("c:\Data1.txt");
           file.write("Guru99");
           file.close();
    }
    catch(IOException){}
  }
}

If you do not  handle the exception in a try catch block , compiling will fail. But almost every other method in the java library or even user defined may throw an exception or two. Handling all the exceptions using the try and catch block could be cumbersome and will hinder the coders throughput.
So java provides an option , wherein whenever you are using a risky piece of code in the method definition you  declare it throws an exception without implementing try catch.

Syntax

method (Arguments) throws Exception1,Exception2,Exception,… {}

Consider the same example as above with throws in method declaration.

import java.io.*;
class file1{
    public static void main(String[] args) throws IOException{
      FileWriter file = new FileWriter("c:\Data1.txt");
      file.write("Guru99");
      file.close();
    }
}

Note: To successfully the above codes , first create an empty text file with name Data1.txt in your C drive.
In sum, there are two methods to handle Exceptions.

1. Put the Exception causing code in try and catch block.
2. Declare the method to be throwing an Exception

If either of the above two is not done, compiler gives an error. The idea behind enforcing this rule is that you as a programmer are aware that a certain piece of code could be risky and may throw an exception.
Trivia

What is the difference between throw and throws?

throw : It is used to create a new Exception object and throw it
throws : is used in method definition , to declare that a risky method is being called .