☕ Java MCQ Questions – Page 147

public class Test {
    public static void main(String[] args) {
        String[] names = new String[3];
        names[0] = "Alice";
        names[1] = "Bob";
        System.out.println(names[2]);
    }
}

import java.util.LinkedList;

public class Test {
    public static void main(String[] args) {
        LinkedList<String> names = new LinkedList<>();
        names.add("Alice");
        names.add("Bob");
        names.trimToSize();
        System.out.println(names.size());
    }
}

import java.util.LinkedList;

public class MyClass {
    public static void main(String[] args) {
        LinkedList<String> list = new LinkedList<>();
        String element = list.peek(); // Returns null if list is empty
        System.out.println(element.length());
    }
}

import java.util.ArrayList;

public class Question1 {
    public static void main(String[] args) {
        ArrayList<int> numbers = new ArrayList<>();
        numbers.add(10);
        System.out.println(numbers);
    }
}

class A {
    A(int x) {}
}

class B extends A {
    B() {
        System.out.println("Hello from B constructor");
        super(5);
    }
}

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

public class InvalidFileNameCanonical {
    public static void main(String[] args) {
        // On Windows, characters like ':', '<', '>', '"', '|', '?', '*' are invalid in filenames.
        // Using ':' within a filename component usually leads to an IOException.
        File invalidFile = new File("C:\\temp\\invalid:filename.txt");
        try {
            System.out.println("Canonical path: " + invalidFile.getCanonicalPath());
        } catch (IOException e) {
            System.out.println("Error: " + e.getClass().getSimpleName() + ": " + e.getMessage());
        }
    }
}

import java.util.LinkedList;

public class MyClass {
    public static void main(String[] args) {
        LinkedList<Boolean> flags = new LinkedList<>();
        flags.add(true);
        flags.add(false);
        flags.clear();
        System.out.println(flags.isEmpty());
    }
}

public class MyThread implements Runnable {
    @Override
    public void run() {
        System.out.println("Thread is running...");
    }

    public static void main(String[] args) {
        MyThread myRunnable = new MyThread();
        Thread t = new Thread(myRunnable);
        t.start();
        t.start(); // Attempt to start the same thread again
    }
}

import java.io.BufferedReader;
import java.io.StringReader;
import java.io.IOException;

public class MyClass {
    public static void main(String[] args) {
        try {
            BufferedReader br = new BufferedReader(new StringReader("A"));
            char c = br.read();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.util.TreeSet;

class Item implements Comparable<Item> {
    String name;
    public Item(String name) { this.name = name; }
    @Override
    public int compareTo(Item other) {
        return this.name.compareTo(other.name);
    }
}

public class Main {
    public static void main(String[] args) {
        TreeSet<Item> items = new TreeSet<>();
        items.add(new Item("Apple"));
        items.add(new Item(null));
        System.out.println(items.size());
    }
}

public class TypeCast {
    public static void main(String[] args) {
        byte b = 75;
        short s = b;
        System.out.println(s);
    }
}

public class MyRunnable implements Runnable {
    @Override
    public void run() {
        System.out.println("Runnable object trying to wait on itself.");
        try {
            // 'this' refers to the MyRunnable instance, not the Thread
            this.wait(); 
        } catch (InterruptedException e) {
            System.out.println("Interrupted");
        }
    }

    public static void main(String[] args) {
        MyRunnable myRunnable = new MyRunnable();
        new Thread(myRunnable).start();
    }
}

import java.util.Date;

class MutableData {
    private Date value;
    public MutableData(Date value) { this.value = value; }
    public Date getValue() { return value; }
    public void setValue(Date value) { this.value = value; }

    // No implements Cloneable
    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone(); // Calling Object's clone without implementing Cloneable
    }
}

public class CloneErrorExample {
    public static void main(String[] args) {
        MutableData data = new MutableData(new Date());
        try {
            MutableData clonedData = (MutableData) data.clone();
        } catch (CloneNotSupportedException e) {
            System.out.println("Caught: " + e.getMessage());
        }
    }
}

public class LoopError {
    public static void main(String[] args) {
        int count;
        do {
            count = 1;
            System.out.println(count);
        } while (count < 3);
    }
}

public class Main {
    public static void main(String[] args) {
        Runnable task = () -> {
            try {
                Thread.sleep(50); // Simulate some work
                System.out.println("Task completed after delay.");
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        };
        new Thread(task).start();
        System.out.println("Main thread continues immediately.");
    }
}

public class Test {
    public static void main(String[] args) {
        char[] letters = {'a', 'b', 'c'};
        System.out.println(letters.length);
    }
}

import java.util.HashSet;

public class Test {
    public static void main(String[] args) {
        HashSet<String> fruits = new HashSet<>();
        fruits.add("Apple");
        fruits.add("Banana");
        System.out.println(fruits.contains("Apple"));
        System.out.println(fruits.contains("Orange"));
    }
}