Interview question

What is the difference between checked and unchecked exceptions in Java? Java में checked और unchecked exceptions में क्या अंतर है?

Answer

Type	Checked at	Must be declared/caught?	Examples
Checked exception	Compile time	Yes - or method must declare 'throws'	IOException, SQLException
Unchecked exception	Runtime only	No - compiler doesn't enforce handling	NullPointerException, ArithmeticException

import java.io.*;

// Checked exception - compiler FORCES you to handle or declare it
public void readFile() throws IOException {  // must declare
    FileReader file = new FileReader('data.txt');
}

// Or handle it directly
public void readFileSafe() {
    try {
        FileReader file = new FileReader('data.txt');
    } catch (IOException e) {
        System.out.println('File error: ' + e.getMessage());
    }
}

// Unchecked exception - compiler does NOT force handling
public void divide(int a, int b) {
    int result = a / b;  // no try-catch or throws required
}
// If b is 0, throws ArithmeticException at RUNTIME, not caught at compile time

// Class hierarchy:
// Throwable
//   -> Exception (checked, unless it extends RuntimeException)
//        -> RuntimeException (unchecked)
//   -> Error (unchecked, serious JVM-level problems, e.g. OutOfMemoryError)

Type	कब check होता है	Handle करना ज़रूरी?	उदाहरण
Checked	Compile time	हाँ	IOException, SQLException
Unchecked	सिर्फ Runtime	नहीं	NullPointerException

import java.io.*;

public void readFile() throws IOException {
    FileReader file = new FileReader('data.txt');
}

public void readFileSafe() {
    try {
        FileReader file = new FileReader('data.txt');
    } catch (IOException e) {
        System.out.println('File error: ' + e.getMessage());
    }
}

public void divide(int a, int b) {
    int result = a / b;  // try-catch ज़रूरी नहीं
}
// b शून्य हो तो RUNTIME पर ArithmeticException

// Class hierarchy:
// Throwable -> Exception (checked) -> RuntimeException (unchecked)
//           -> Error (unchecked, serious JVM problems)

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