☕ Java MCQ Questions – Page 50

public class UnreachableCodeLoop {
    public static void main(String[] args) {
        for (int i = 0; i < 3; i++) {
            System.out.println("Iteration " + i);
            break;
            System.out.println("This message is unreachable.");
        }
    }
}

import java.io.IOException;

class CustomProcessException extends Exception {
    public CustomProcessException(String message) { super(message); }
}

public class Main {
    public static void performAction() throws CustomProcessException {
        throw new CustomProcessException("Action failed");
    }

    public static void main(String[] args) {
        try {
            performAction();
        } catch (IOException e) { // This catch block is for IOException, not CustomProcessException
            System.out.println("Caught IO Exception: " + e.getMessage());
        }
    }
}

package model;

public class SecretData {
    private SecretData() { // Private constructor
        System.out.println("SecretData instance created.");
    }

    public static SecretData createInstance() {
        return new SecretData();
    }
}

package client;
import model.SecretData;

public class App {
    public static void main(String[] args) {
        SecretData data = new SecretData(); // Attempt to call private constructor
    }
}

import java.io.BufferedWriter;
import java.io.StringWriter;
import java.io.IOException;

public class Test {
    public static void main(String[] args) {
        StringWriter sw = new StringWriter();
        try (BufferedWriter bw = new BufferedWriter(sw)) {
            char[] data = {'H', 'e', 'l', 'l', 'o'};
            bw.write(data, 0, 10); // Attempt to write more chars than available
            bw.flush();
        } catch (IOException e) {
            System.err.println("IO Error: " + e.getMessage());
        } catch (IndexOutOfBoundsException e) {
            System.err.println("Array Access Error: " + e.getClass().getName());
        }
        System.out.println("Content: " + sw.toString());
    }
}

import java.util.HashSet;
import java.util.Set;

public class MyClass {
    public static void main(String[] args) {
        Set<Object> data = new HashSet<>();
        data.add("String Data");
        data.add(123);
        
        for (Object item : data) {
            Integer value = (Integer) item; // This line will cause an error for "String Data"
            System.out.println(value);
        }
    }
}

import java.io.*;

class Singleton implements Serializable {
    private static final long serialVersionUID = 1L;
    private static Singleton INSTANCE = new Singleton();
    private int value = 0;

    private Singleton() {
        System.out.println("Singleton constructor called.");
    }

    public static Singleton getInstance() {
        return INSTANCE;
    }

    public void setValue(int v) { this.value = v; }
    public int getValue() { return value; }

    protected Object readResolve() {
        System.out.println("readResolve called.");
        return INSTANCE;
    }
}

public class SerializationTest {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        Singleton original = Singleton.getInstance();
        original.setValue(100);

        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(bos);
        oos.writeObject(original);
        oos.close();

        Singleton originalAfterSerialization = Singleton.getInstance();
        originalAfterSerialization.setValue(200);

        ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
        ObjectInputStream ois = new ObjectInputStream(bis);
        Singleton deserialized = (Singleton) ois.readObject();
        ois.close();

        System.out.println("Original Value: " + original.getValue());
        System.out.println("Deserialized Value: " + deserialized.getValue());
        System.out.println("Are same instances: " + (original == deserialized));
    }
}

import java.io.IOException;

class Super {
    void method() throws IOException {
        System.out.println("Super method");
    }
}

class Sub extends Super {
    @Override
    void method() throws Exception {
        System.out.println("Sub method");
    }
}

public class Main {
    public static void main(String[] args) {
        Super s = new Sub();
        try {
            s.method();
        } catch (Exception e) {
            System.out.println("Caught exception");
        }
    }
}

public class Test {
    public static int getValue() {
        try {
            System.out.print("Try ");
            return 10;
        } finally {
            System.out.print("Finally ");
            return 20;
        }
    }
    public static void main(String[] args) {
        System.out.println(getValue());
    }
}

import java.time.LocalDate;

public class LocalDateImmutability {
    public static void main(String[] args) {
        LocalDate date1 = LocalDate.of(2023, 1, 15);
        LocalDate date2 = date1.plusDays(10);
        System.out.println(date1.getDayOfMonth());
    }
}

import java.io.FileReader;
import java.io.IOException;
import java.io.File;

public class FileReaderError1 {
    public static void main(String[] args) {
        File dir = new File("temp_directory_fr");
        dir.mkdir(); // Ensure directory exists

        try (FileReader fr = new FileReader(dir)) { // Attempt to open a directory as a file
            int data = fr.read();
            System.out.println("Read: " + (char)data);
        } catch (IOException e) {
            System.err.println(e.getClass().getSimpleName());
        } finally {
            dir.delete(); // Clean up
        }
    }
}

class EmptyInputException extends RuntimeException {
    // No constructor explicitly defined
}

public class Main {
    public static void main(String[] args) {
        try {
            throw new EmptyInputException();
        } catch (EmptyInputException e) {
            System.out.println("Error: " + e.getMessage());
        }
    }
}

public class LoopTest {
    public static void main(String[] args) {
        int i = 0;
        do {
            i++;
        } while (i < 2);
        break;
    }
}