☕ Java MCQ Questions – Page 140

abstract class Shape {
    public final abstract double getArea();
}

class Circle extends Shape {
    private double radius;
    public Circle(double radius) { this.radius = radius; }
    @Override
    public double getArea() { return Math.PI * radius * radius; }
}

public class ErrorTest {
    public static void main(String[] args) {
        // Code would be here if no error
    }
}

public class ExceptionTest {
    public static void main(String[] args) {
        try {
            throw new NullPointerException();
        } catch (Exception e) {
            System.out.println("Caught Exception");
        } catch (Throwable t) {
            System.out.println("Caught Throwable");
        }
    }
}

public class ThreadStateDemo1 {
    public static void main(String[] args) throws InterruptedException {
        Thread t = new Thread(() -> System.out.println("Thread running."));
        System.out.println("1: " + t.getState());
        t.start();
        System.out.println("2: " + t.getState());
        Thread.sleep(100); // Give thread time to finish
        System.out.println("3: " + t.getState());
    }
}

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class Test {
    public static void main(String[] args) {
        List<String> fruits = new ArrayList<>();
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Cherry");
        Iterator<String> it = fruits.iterator();
        StringBuilder sb = new StringBuilder();
        while (it.hasNext()) {
            sb.append(it.next()).append(" ");
        }
        System.out.println(sb.toString().trim());
    }
}

public class TypeCast {
    public static void main(String[] args) {
        float value = 123.45f;
        long l = (long) value;
        System.out.println(l);
    }
}

public class MyClass {
    public static void main(String[] args) {
        StringBuffer sb = new StringBuffer("Programming");
        sb.replace(12, 15, "Code");
        System.out.println(sb);
    }
}

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class Test {
    public static void main(String[] args) {
        List<Double> grades = new ArrayList<>();
        grades.add(90.5);
        grades.add(85.0);
        Iterator<Double> it = grades.iterator();
        it.next(); 
        it.remove(); 
        try {
            it.remove(); 
        } catch (IllegalStateException e) {
            System.out.println("Caught: " + e.getClass().getSimpleName());
        }
    }
}

interface MyRunnable {
    void run();
}

class BasePrinter {
    public void printBase() { System.out.println("Base Print"); }
}

class DerivedPrinter extends BasePrinter {
    public void printDerived() {
        MyRunnable r = () -> {
            super.printBase(); // Attempting to use 'super'
        };
        r.run();
    }
}

public class Main {
    public static void main(String[] args) {
        new DerivedPrinter().printDerived();
    }
}

public class Main {
    public static void main(String[] args) {
        int[][] data = {{1, 2}, {3, 4}};
        data[0][0] = 10;
        System.out.println(data[0][0] + data[0][1]);
    }
}

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

public class HashSetError3 {
    public static void main(String[] args) {
        Set<String> fruits = new HashSet<>();
        fruits.add("Apple");
        fruits.add("Banana");

        Set<String> unmodifiableFruits = Collections.unmodifiableSet(fruits);
        unmodifiableFruits.add("Cherry"); // ERROR line
        System.out.println(unmodifiableFruits);
    }
}

import java.io.FileWriter;
import java.io.IOException;

public class FileWriterTest {
    public static void main(String[] args) {
        try (FileWriter writer = new FileWriter("output.txt")) {
            writer.write("Hello");
            writer.write(" World");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

public class Question2 {
    public static void main(String[] args) {
        ArrayList<String> names = new ArrayList<>();
        names.add("Alice");
        System.out.println(names);
    }
}

public class InvalidPriority {
    public static void main(String[] args) {
        Thread t = new Thread(() -> {
            System.out.println("Thread running");
        });
        t.setPriority(11); // Priority must be between Thread.MIN_PRIORITY (1) and Thread.MAX_PRIORITY (10)
        t.start();
    }
}

class Printer {
    void print(int i) {
        System.out.println("Printing int: " + i);
    }
    void print(double d) {
        System.out.println("Printing double: " + d);
    }
    void print(String s) {
        System.out.println("Printing String: " + s);
    }
}

public class Main {
    public static void main(String[] args) {
        Printer p = new Printer();
        p.print(10);
        p.print("Hello");
        p.print(5.5f); // float will be promoted to double
    }
}

public class ArrayShallowCopy {
    public static void main(String[] args) {
        StringBuilder[] sba1 = {new StringBuilder("A"), new StringBuilder("B")};
        StringBuilder[] sba2 = sba1.clone();
        sba2[0].append("C");
        sba2[1] = new StringBuilder("D");
        System.out.println(sba1[0] + " " + sba1[1]);
    }
}