☕ Java MCQ Questions – Page 53

public class ArrayError {
    public static void main(String[] args) {
        int myArray = new int[5];
    }
}

import java.util.function.Predicate;

public class Test {
    public static void main(String[] args) {
        Predicate<Integer> isEven = num -> num % 2 == 0;
        Predicate<Integer> isGreaterThanTen = num -> num > 10;

        System.out.println(isEven.test(12));
        System.out.println(isGreaterThanTen.test(9));
    }
}

import java.io.*;

public class FileWriterError2 {
    public static void main(String[] args) {
        try (FileWriter fw = new FileWriter("testfile.txt")) {
            char[] data = {'H', 'e', 'l', 'l', 'o'}; 
            fw.write(data, 0, 10); // Attempt to write more characters than available
        } catch (IOException | IndexOutOfBoundsException e) {
            System.out.println("Error: " + e.getClass().getSimpleName() + " - " + e.getMessage());
        }
    }
}

import java.util.function.Predicate;

@FunctionalInterface
interface MyValidator {
    boolean validate(String input);
    default void logValidationAttempt();
}

public class Main {
    public static void main(String[] args) {
        // Attempt to use MyValidator
    }
}

import java.io.*;

class NonSerializableField {
    String value;
    public NonSerializableField(String value) { this.value = value; }
}

class Container implements Serializable {
    String id;
    NonSerializableField field;
    public Container(String id, String value) {
        this.id = id;
        this.field = new NonSerializableField(value);
    }
}

public class DeserializationError2 {
    public static void main(String[] args) {
        byte[] data = null;
        try (ByteArrayOutputStream bos = new ByteArrayOutputStream();
             ObjectOutputStream oos = new ObjectOutputStream(bos)) {
            Container container = new Container("C1", "Data");
            oos.writeObject(container);
            data = bos.toByteArray();
        } catch (IOException e) {
            System.out.println("Error: " + e.getClass().getName() + ": " + e.getMessage());
        }
    }
}

public class Main {
    public static void main(String[] args) {
        int[][] matrix = {{1, 2}, {3, 4, 5}};
        System.out.println(matrix[1].length);
    }
}

public class MultiArrayQ10 {
    public static void main(String[] args) {
        int[][][] cube = new int[2][][];
        cube[0] = new int[2][3];
        cube[1] = new int[1][1];
        cube[0][0][0] = 10;
        try {
            System.out.println(cube[1][0][1]);
        } catch (ArrayIndexOutOfBoundsException e) {
            System.out.println("AIOOBE caught");
        } catch (Exception e) {
            System.out.println(e.getClass().getSimpleName());
        }
        System.out.println(cube[0][0][0]);
    }
}

public class FinalPrimitiveReassignment {
    public static void main(String[] args) {
        final int count = 5;
        count = 10;
        System.out.println(count);
    }
}

import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Comparator;

public class PriorityQueueCustomOrdering {
    public static void main(String[] args) {
        Queue<String> pq = new PriorityQueue<>(Comparator.reverseOrder());
        pq.offer("apple");
        pq.offer("banana");
        pq.offer("cherry");
        System.out.println(pq.poll());
        System.out.println(pq.peek());
    }
}

import java.io.*;

class Address {
    String street;
    Address(String street) { this.street = street; }
}

class Student implements Serializable {
    String name;
    Address address;

    public Student(String name, String street) {
        this.name = name;
        this.address = new Address(street);
    }
}

public class Main {
    public static void main(String[] args) {
        Student s = new Student("Alice", "123 Main St");
        try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("student.ser"))) {
            oos.writeObject(s);
        } catch (IOException e) {
            System.err.println(e.getClass().getSimpleName() + ": " + e.getMessage());
        }
    }
}

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

public class FileReaderError2 {
    public static void main(String[] args) {
        File file = new File("test_fr2.txt");
        try {
            file.createNewFile();
            try (FileReader fr = new FileReader(file)) {
                fr.close(); // Close the stream
                int data = fr.read(); // Attempt to read after closing
                System.out.println("Read: " + (char)data);
            }
        } catch (IOException e) {
            System.err.println(e.getClass().getSimpleName() + ": " + e.getMessage());
        } finally {
            file.delete();
        }
    }
}

class Counter {
    int count = 0;
    public static void increment() {
        count++;
    }
}

public class Main {
    public static void main(String[] args) {
        Counter.increment();
    }
}

class Parent {
    public void startProcess() {
        System.out.println("Parent process started.");
    }
}

class Child extends Parent {
    @Override
    public void startProcass() {
        System.out.println("Child process started.");
    }
}

import java.util.TreeMap;

public class Test {
    public static void main(String[] args) {
        TreeMap<String, Integer> map = new TreeMap<>();
        map.put("A", 1);
        map.put("B", 2);

        Integer oldVal1 = map.replace("A", 10); // Replaces 1 with 10
        boolean replaced2 = map.replace("B", 20, 200); // Fails, old value is 2, not 20
        boolean replaced3 = map.replace("C", 3, 30); // Fails, key C does not exist
        Integer oldVal4 = map.replace("D", 4); // Returns null, key D does not exist

        System.out.println(oldVal1 + ", " + replaced2 + ", " + replaced3 + ", " + oldVal4 + ", " + map.get("B"));
    }
}