1Z0-811 Arrays and Methods — Timed 10 Questions

Question 1

A method 'public static int findMax(int[] numbers)' returns the maximum value in the array. Which implementation correctly handles an empty array by returning 0?

Accepted Answer

if(numbers.length == 0) return 0; int max = numbers[0]; for(int i=1; i<numbers.length; i++) if(numbers[i] > max) max = numbers[i]; return max;. Ly handles an empty array by checking `numbers.length == 0` and returning 0 before attempting to access `numbers[0]`, which would throw an `ArrayIndexOutOfBoundsException` on an empty array. It then initializes `max` to the first element and iterates from index 1, ensuring all elements are compared correctly even if all numbers are negative.

Answer

int max = 0; for(int n: numbers) if(n > max) max = n; return max;

Answer

int max = numbers[0]; for(int i=1; i<numbers.length; i++) if(numbers[i] > max) max = numbers[i]; return max;

Answer

if(numbers.length == 0) return 0; int max = 0; for(int n: numbers) if(n > max) max = n; return max;

Question 2

Which THREE statements are correct about the 'main' method signature in Java?

Accepted Answer

It must be declared public.. Option A is correct because the JVM launcher requires the entry-point method to be public so it can be invoked from outside the class. Option C is correct because the main method must be declared void; the JVM does not use a return value from it. Option D is correct because main must be static so the JVM can call it without instantiating the class. Option B is incorrect because a main method returning int is not recognized as the standard entry point. Option E is incorrect because the method must be named exactly main, not any valid identifier.

Answer

It can be declared to return an int.

Answer

It can be named any valid identifier.

Question 3

Match each control flow statement to its purpose.

Accepted Answer

if-else: Executes a block of code based on a boolean condition.. The correct matches are: if-else (A) executes based on condition, switch (B) selects based on value, for loop (C) repeats fixed times, while loop (D) repeats while condition true. Options E and F are incorrect because they misassign the purposes.

Answer

if-else: Repeats a block of code a fixed number of times.

Answer

switch: Repeats a block of code as long as a condition is true.

Question 4

A method is designed to compute the average of an array of test scores. What should the method return if the array is empty (length 0)?

Accepted Answer

Return 0.0. The method should return 0.0 for an empty array to avoid division by zero and to provide a safe default value. In Java, an empty array has length 0, and computing the average would require dividing by zero, which throws an ArithmeticException. Returning 0.0 is a common convention for empty collections, as it allows the caller to handle the result gracefully without crashing.

Answer

Do not compile; requires a return of type double

Answer

Throw a RuntimeException

Answer

Return null

Question 5

An application requires storing a fixed set of 12 monthly temperatures. Which initialization is most appropriate?

Accepted Answer

double[] temps = {15.5, 16.2, 18.0, 20.1, 23.4, 27.8, 30.0, 29.5, 26.2, 22.0, 18.5, 16.0};. It initializes a fixed-size array of 12 doubles with the actual monthly temperature values in a single statement, which is the most appropriate for storing a fixed set of 12 values. The array size is implicitly determined by the number of elements in the initializer list, and the syntax is concise and readable for this use case.

Answer

ArrayList temps = new ArrayList<>();

Answer

double[] temps = new double[12];

Answer

double temps[] = {0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0};

Question 6

A method is declared as: public static int[] generateSequence(int n) { ... }. Which return statement is valid inside this method?

Accepted Answer

return new int[n];. The method's return type is `int[]`, meaning it must return a reference to an integer array. Option B, `return new int[n];`, creates an array of length `n` and returns it, which is valid. Option D, `return new int[0];`, also creates an integer array (of length 0) and returns it, which is syntactically valid as well. Options A and C are invalid because they return primitive `int` values, not `int[]` references. Therefore, both B and D are correct return statements.

Answer

return result; where result is an int variable

Answer

return 0;

Question 7

A programmer writes code to transpose a 2D array (matrix). Given: int[][] matrix = {{1,2},{3,4}}; int[][] result = new int[2][2]; for (int i=0; i<2; i++) for (int j=0; j<2; j++) result[j][i] = matrix[i][j]; What is the value of result[1][0]?

Accepted Answer

2. The code transposes the matrix by assigning matrix[i][j] to result[j][i]. For result[1][0], we need the value where j=1 and i=0, which comes from matrix[0][1] = 2. Thus, result[1][0] = 2, making option C correct.

Answer

4

Answer

3

Answer

1

Question 8

What is printed when the main method runs?

Accepted Answer

5. The method `modifyArray` receives a reference to the array, and the assignment `arr = new int[]{100};` changes the local reference `arr` to point to a new array object. The original array in `main` remains unchanged, so `arr[0]` still prints 5. Java passes object references by value, meaning the reference itself is copied, and reassigning the local reference does not affect the caller's reference.

Answer

0

Answer

Compilation error: cannot assign new array to parameter

Answer

100