☕ Java MCQ Questions – Page 157

public class Test {
    public static void main(String[] args) {
        char[] data = {'1', '2', '3', '4', '5'};
        StringBuilder sb = new StringBuilder("Start Middle End");
        String replacement = new String(data, 1, 3);
        sb.replace(6, 12, replacement);
        System.out.println(sb);
    }
}

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

class FaultyIterable<T> implements Iterable<T> {
    private List<T> data;
    public FaultyIterable(List<T> data) { this.data = new ArrayList<>(data); }

    @Override
    public Iterator<T> iterator() {
        return new Iterator<T>() {
            private int currentIndex = 0;
            @Override
            public boolean hasNext() { return currentIndex <= data.size(); } // Incorrect condition
            @Override
            public T next() {
                if (currentIndex >= data.size()) {
                    throw new java.util.NoSuchElementException();
                }
                return data.get(currentIndex++);
            }
        };
    }
}
public class IteratorFaultyHasNext {
    public static void main(String[] args) {
        FaultyIterable<Integer> myIterable = new FaultyIterable<>(Arrays.asList(10, 20));
        Iterator<Integer> it = myIterable.iterator();
        it.next(); // 10
        it.next(); // 20
        it.next(); // Error here
    }
}

import java.util.TreeMap;

public class Main {
    public static void main(String[] args) {
        TreeMap<Integer, String> map = new TreeMap<>();
        map.put(10, "A");
        map.put(20, "B");
        map.put(30, "C");
        String nonComparableKey = "Five";
        map.headMap(nonComparableKey); // Intentional error point
    }
}

public class LoopError {
    public static void main(String[] args) {
        int data = 100;
        for (int val : data) {
            System.out.println(val);
        }
    }
}

public class NullThreadStart {
    public static void main(String[] args) {
        Thread myThread = null;
        myThread.start(); // Calling method on a null reference
    }
}

class Message {
    String content;

    public Message(String content) {
        this.content = content;
    }

    public String getContent() {
        return "Message: " + content;
    }
}

public class Main {
    public static void main(String[] args) {
        System.out.println(new Message("Hello World").getContent());
    }
}

public class Test {
    public static void main(String[] args) {
        String result = "";
        for (int i = 0; i < 2; i++) {
            for (int j = 0; j < 2; j++) {
                if (i == 0 && j == 1) {
                    break;
                }
                if (i == 1 && j == 0) {
                    continue;
                }
                result += "(" + i + "," + j + ")";
            }
        }
        System.out.print(result);
    }
}

import java.util.LinkedList;

public class MyClass {
    public static void main(String[] args) {
        LinkedList<String> names = new LinkedList<>();
        names.add("Alice");
        names.add("Bob");
        names.add(3, "Charlie"); // Invalid index
        System.out.println(names);
    }
}

import java.util.TreeMap;
import java.util.NavigableMap;

public class Test {
    public static void main(String[] args) {
        TreeMap<Integer, String> map = new TreeMap<>();
        map.put(1, "A");
        map.put(2, "B");
        map.put(3, "C");
        map.put(4, "D");
        map.put(5, "E");

        NavigableMap<Integer, String> subMap = map.subMap(2, true, 4, false);
        subMap.put(2, "X"); // Modifies original map
        subMap.remove(3);   // Modifies original map
        System.out.println(map.keySet());
    }
}

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

public class GenericsExample {
    public static void main(String[] args) {
        List<? extends Number> list1 = new ArrayList<Integer>();
        List<Integer> intList = new ArrayList<>();
        intList.add(1);
        intList.add(2);
        List<? extends Number> list2 = intList;
        System.out.println(list2.get(0));
    }
}

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

public class Test {
    public static void main(String[] args) {
        StringWriter sw = new StringWriter();
        try (BufferedWriter bw = new BufferedWriter(sw)) {
            bw.write("Data");
            if (true) throw new IOException("Simulated error");
        } catch (IOException e) {
            System.out.println("Caught exception: " + e.getMessage());
        }
        System.out.println("Content: " + sw.toString());
    }
}

String message = "  Hello World  ";
String processed = message.trim().replace("o", "X").toUpperCase();
System.out.println(processed + " " + message.contains("World"));

public class ArrayError {
    public static void main(String[] args) {
        String[] names = new String[5];
        System.out.println(names[-1]);
    }
}

class A {}
class B {}

class C extends A, B {
    // Class C attempting to extend multiple classes
}

public class Main {
    public static void main(String[] args) {
        C obj = new C();
    }
}