Find error

Question 1

public class FindTheError {
public static void main(String[] args) {
myMethod(0);
}

public static void myMethod(int num) {
    System.out.print(num + " ");
    myMethod(num + 1);    // ❌ no termination
} }

Answer 1

Error: myMethod never stops calling itself—there’s no base case—so you get a StackOverflowError.

Fix: Add a base‑case check before the recursive call,

Question 2

int[] numbers = { 8, 0, 9, 4, 3, 7, 2 };
int location = IntBinarySearcher.search(numbers, 7);

Answer 2

: Binary search requires the array to be sorted, but numbers isn’t sorted.

Fix: Sort first (e.g. Arrays.sort(numbers)), or use a linear search if the data must stay unsorted.

Question 3

ArrayList myList = new ArrayList<String>();</String>

Answer 3

Left side omits the generic parameter.

ArrayList<String> myList = new ArrayList<>();</String>

Question 4

public <T implements Comparable<T>> T greatest(T arg1, T arg2)</T>

Answer 4

Error: Use extends (not implements) in a generic bound.

Fix: public <T extends Comparable<T>> T greatest(T arg1, T arg2)</T>

Question 5

public class MyClass<T> {
public static void displayValue(T value) { … }
}</T>

Answer 5

Error: A static method cannot use the class’s type parameter T.

Fix: Either remove static or give the method its own type parameter:

public static <T> void displayValue(T value) { … }</T>

Question 6

public class Point<T> { … }</T>

Answer 6

Error: You can’t combine extends and super in a type‑parameter declaration.

Fix: Decide on a single bound,

public class Point<T> { … }</T>

Question 7

Node ref = myList;
ref++; // ❌ invalid
System.out.print(ref.value);

Answer 7

Error: You can’t ++ a reference.

Fix:
Advance via the link: ref = ref.next;

Question 8

Node ref = myList;
while (ref.next != null) {
System.out.print(ref.value + “ “);
ref = ref.next;
}

Answer 8

Error: The last node’s value never prints (loop stops when ref.next is null).

Fix:
After the loop, print ref.value, or use while (ref != null).

Question 9

int pop() {
if (top == 0) throw new EmptyStackException();
else {
return s[top - 1];
top–; // ❌ unreachable
}
}

Answer 9

Error: top– is after return.

Fix:
top–;
return s[top];

Question 10

void enqueue(int x) {
if (empty()) {
rear = new Node(x);
front = rear;
} else {
rear = new Node(x);
rear = rear.next; // ❌ loses the new node
}
}

Answer 10

Error: Overwrites rear instead of linking the new node.

Fix:
rear.next = new Node(x);
rear = rear.next;

Question 11

int pop() {
if (empty()) throw new EmptyStackException();
return top.value; // ❌ top never moves
}

Answer 11

Error: Does not update top to remove the node.

Fix:
int val = top.value;
top = top.next;
return val;

Question 12

int dequeue() {
if (empty()) throw new EmptyQueueException();
int value = front.value;
front++; // ❌ invalid pointer arithmetic
return value;
}

Answer 12

Error: front++ isn’t how you advance a node pointer.

Fix:
int value = front.value;
front = front.next;
return value;

Question 13

int dequeue() {
if (empty()) throw new EmptyQueueException();
int val = q[rear]; // ❌ should use front
rear++;
return val;
}

Answer 13

Error: Uses rear instead of front to remove.

Fix:

int val = q[front];
front++;
return val;