Being Code Expert: Exception Handling Using Throws keyword

Throws is a keyword used to indicate that this method could throw this type of exception.

The caller has to handle the exception using a try-catch block or propagate the exception. We can throw either checked or unchecked exceptions. We use the keyword throws to throw the checked exception up the stack to the calling method to handle.

Example 1:

Java

package com.prac;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;

public class ThrowsException {
    public static void main(String[] args) throws FileNotFoundException {
        readFile();
    }

    public static void readFile() throws FileNotFoundException {
        String fileName = "file";
        File file = new File(fileName);
        @SuppressWarnings({ "unused", "resource" })
        FileInputStream stream = new FileInputStream(file);
    }
}

Output

Exception in thread "main" java.io.FileNotFoundException: file (The system cannot find the file specified)
	at java.base/java.io.FileInputStream.open0(Native Method)
	at java.base/java.io.FileInputStream.open(FileInputStream.java:211)
	at java.base/java.io.FileInputStream.<init>(FileInputStream.java:153)
	at com.prac.ThrowsException.readFile(ThrowsException.java:16)
	at com.prac.ThrowsException.main(ThrowsException.java:9)

Example 2:

Java


import java.io.IOException;

class Testthrows {
    void m() throws IOException {
        throw new IOException("Throw exception"); // checked exception
    }

    void n() throws IOException {
        m();
    }

    void p() {
        try {
            n();
        } catch (Exception e) {
            System.out.println("exception handled");
        }
    }

    public static void main(String args[]) {
        Testthrows obj = new Testthrows();
        obj.p();
        System.out.println("normal flow...");
    }
}