AP Computer Science A Medium practice

A recursive method and an iterative method both solve the same problem. Which of the following is a trade-off of choosing recursion over iteration?

What is the output of the following code?

ArrayList<Integer> a = new ArrayList<>();
a.add(1); a.add(2); a.add(3);
ArrayList<Integer> b = new ArrayList<>(a);
b.add(4);
System.out.println(a.size());
System.out.println(b.size());

What is the output of the following code?

int n = 100;
int count = 0;
while (n > 1) {
    n /= 2;
    count++;
}
System.out.println(count);

An abstract class Figure is defined as:

public abstract class Figure {
    public abstract double area();
    public void printArea() {
        System.out.println("Area: " + area());
    }
}

Which of the following statements is true?

What is the output of the following code?

public class Counter {
    private int count;
    
    public Counter(int start) {
        count = start;
    }
    
    public Counter add(int n) {
        count += n;
        return this;
    }
    
    public int getCount() { return count; }
}

// In main:
Counter c = new Counter(0);
System.out.println(c.add(3).add(4).getCount());

A method receives a 2D array and should return the largest value in the array. Which implementation is correct?

public static int findMax(int[][] arr) {
    int max = arr[0][0];
    for (int[] row : arr) {
        for (int val : row) {
            if (val > max) max = val;
        }
    }
    return max;
}

What is the value of n after the following code executes?

int n = (int)(Math.random() * 6) + 1;

What is the output of the following code?

int a = 2;
System.out.println(a++);
System.out.println(a);

Consider the following recursive method:

public static int sumArray(int[] arr, int index) {
    if (index == arr.length) return 0;
    return arr[index] + sumArray(arr, index + 1);
}

What is returned by sumArray(new int[]{3, 1, 4, 1, 5}, 0)?

What is the output of the following code?

int x = 0;
if (x = 5) {
    System.out.println("hello");
}

What is the output of the following code?

int[][] g = new int[2][3];
for (int r = 0; r < g.length; r++) {
    for (int c = 0; c < g[r].length; c++) {
        g[r][c] = r + c;
    }
}
System.out.println(g[1][2]);

What is the output of the following code?

int[] arr = {1, 2, 3, 4, 5};
for (int i = 0; i < arr.length / 2; i++) {
    int temp = arr[i];
    arr[i] = arr[arr.length - 1 - i];
    arr[arr.length - 1 - i] = temp;
}
System.out.println(arr[0] + " " + arr[2] + " " + arr[4]);

What is printed by the following code?

public class Temp {
    private double celsius;
    
    public Temp(double c) { celsius = c; }
    
    public double toFahrenheit() {
        return celsius * 9 / 5 + 32;
    }
    
    public String toString() {
        return celsius + "C";
    }
}

// In main:
Temp t = new Temp(100);
System.out.println(t);
System.out.println(t.toFahrenheit());

What is the output of the following code?

int[][] t = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
for (int c = 0; c < t[0].length; c++) {
    for (int r = 0; r < t.length; r++) {
        System.out.print(t[r][c] + " ");
    }
}

What is the output of the following code?

int x = 5;
while (true) {
    if (x <= 0) break;
    System.out.print(x + " ");
    x -= 2;
}