Java Community | Help. Code. Learn.•5d ago

Throw and Throws

I am learning Exception Handling in Java and stuck with Throw and Throws As I am not getting when to use throw and when to use throws.

17 Replies

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Dev GuptaOP•5d ago

Help Please

ayylmao123xdd•5d ago

throw is used when you want to throw an exception for example

public void checkIfEqualsFive(int number) {
  if (number != 5) {
    throw new IllegalArgumentException("number must be five")
  }
}

public void checkIfEqualsFive(int number) {
  if (number != 5) {
    throw new IllegalArgumentException("number must be five")
  }
}

throws is used when a method throws a checked exception so you gotta either use try catch or the throws thing like this

public void readFile(String filePath) throws IOException {
//code that reads a file
}

public void readFile(String filePath) throws IOException {
//code that reads a file
}

if you use try catch you dont need the throws in the method because the exception is handled within that try catch or try with resources

Dev GuptaOP•5d ago

Ok let me do it once and get clear @ayylmao123xdd can you give example for second code

ayylmao123xdd•5d ago

try catch or throws

Dev GuptaOP•5d ago

try catch

ayylmao123xdd•5d ago

ok but in like 1h or 2 cuz now im doing some stuff

Dev GuptaOP•5d ago

import java.util.Scanner;

public class Test extends Object{
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        checkIfEqualsFive(n);
        sc.close();
    }

    public static void checkIfEqualsFive(int number) {
        if (number != 5) {
            throw new IllegalArgumentException("number must be five");
       }
    }
}

import java.util.Scanner;

public class Test extends Object{
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        checkIfEqualsFive(n);
        sc.close();
    }

    public static void checkIfEqualsFive(int number) {
        if (number != 5) {
            throw new IllegalArgumentException("number must be five");
       }
    }
}

Check is this correct or the other one for throw keyword

import java.util.Scanner;

public class Test extends Object{
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        try{
            int n=sc.nextInt();
            checkIfEqualsFive(n);
        }
        catch(IllegalArgumentException e){
            System.out.println(e);
        }
        sc.close();
    }

    public static void checkIfEqualsFive(int number) {
        if (number != 5) {
            throw new IllegalArgumentException("number must be five");
       }
    }
}

import java.util.Scanner;

public class Test extends Object{
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        try{
            int n=sc.nextInt();
            checkIfEqualsFive(n);
        }
        catch(IllegalArgumentException e){
            System.out.println(e);
        }
        sc.close();
    }

    public static void checkIfEqualsFive(int number) {
        if (number != 5) {
            throw new IllegalArgumentException("number must be five");
       }
    }
}

Or is this correct for the throw keyword?

ayylmao123xdd•5d ago

this one is good yea this one also works but you could just do like this

 if (number != 5) {
            System.out.println("number must be five");
       }

 if (number != 5) {
            System.out.println("number must be five");
       }

because you are printing it anyway and with try catch let me write it now

Dev GuptaOP•5d ago

This how be use throw keyword?

ayylmao123xdd•5d ago

public void readFile(String filePath) {
  try {
   //code that reads a file 
  } catch (IOException e) {
     // do stuff with the exception
  }
}

public void readFile(String filePath) {
  try {
   //code that reads a file 
  } catch (IOException e) {
     // do stuff with the exception
  }
}

and then you dont need the throws yes

Dev GuptaOP•5d ago

Ok, thank you for clearing the concept

ayylmao123xdd•5d ago

https://tenor.com/view/roblox-script-i-just-write-thousand-line-of-codes-without-a-single-error-coding-hello-world-gif-13384672663063020392

Tenor

ayylmao123xdd•5d ago

heres a gif for u l0l and u should try with other examples too so you remember how to do it

Dev GuptaOP•4d ago

dan1st•4d ago

Maybe the following is simple and explains it (if there are any doubts left): - These are different keywords and you cannot use one instead of the other (or you'll get a compiler error) - throw is for the act of throwing an exception - throws makes a statement that a method might be throwing an (uncaught) exception. Calling another method that might throw an exception without catching it constitutes as such. and you should catch exceptions wherever you feel it's sensible to handle the situation of these exceptions occuring and you always have the option of catching an exception and throwing another one if you want to change the type of the exception

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