2009 FRQ 1 • 10 min read

FRQ #1

import java.lang.Math;

public class NumberCube {
    public int toss() { 
        return 1 + (int)(Math.random() * 6);
    }
} 

a) cubeTosses method

Solution:

import java.lang.Math;

public class NumberCube {
    public int toss() { 
        return 1 + (int)(Math.random() * 6);
    }

    // Begin solution to problem
    public int[] getCubeTosses(NumberCube cube, int numTosses) {
        // Initialize an array of integers with length equal to numTosses
        int[] results = new int[numTosses];
    
        // Loop for numTosses
        for (int i = 0; i < numTosses; i ++) {
            // Set each value to a cube roll; must be done this way because Java arrays are FIXED IN SIZE
            results[i] = cube.toss();
        };
    
        return results;
    }
    // End soluton to problem
};

// Create new object for testing
NumberCube dice = new NumberCube();

// Set results to a variable, because otherwise it returns a memory address/pointer
int[] list = dice.getCubeTosses(dice, 5);

// Print each item in the list
for (int item : list) {
    System.out.println(item);
}

5
6
1
2
3

CollegeBoard Grade:

• 1 for correctly constructing arrays
• 2.5 for functionality
• .5 for return

b) getLongestRun method

Solution:

import java.lang.Math;

public class NumberCube {
    public int toss() { 
        return 1 + (int)(Math.random() * 6);
    }

    public int[] getCubeTosses(NumberCube cube, int numTosses) {
        // Initialize an array of integers with length equal to numTosses
        int[] results = new int[numTosses];
    
        // Loop for numTosses
        for (int i = 0; i < numTosses; i ++) {
            // Set each value to a cube roll; must be done this way because Java arrays are FIXED IN SIZE
            results[i] = cube.toss();
        };
    
        return results;
    }

    // Begin solution to problem
    public static int getLongestRun(int[] values) {
        // If there are no values, return -1
        if (values.length == 0) {
            return -1;
        };
    
        // Create a new integer for the maximum value, zero for default
         int maxIndex = 0;
    
        // For every value
        for (int i = 0; i < values.length; i ++) {
            // If the value is bigger than the current max, replace the max with it
            if (values[maxIndex] < values[i]) {
                maxIndex = i;
            }
        };
    
        // By the end of the loop, the index of the max will be returned
        return maxIndex;
    };
    // End solution to problem
};

// Create new object for testing
NumberCube dice = new NumberCube();

// Set results to a variable, because otherwise it returns a memory address/pointer
int[] list = dice.getCubeTosses(dice, 5);

// Print each item in the list
for (int item : list) {
    System.out.println(item);
}

// Get the index of the max
dice.getLongestRun(list)

3
6
3
1
6





1

CollegeBoard Grading:

• 1 for iteration
• 1 for comparing values
• 1 checks value for each run
• 1 for identifying maximum
• 1 for returning max or -1

(Initially, I would have only gotten 2 points because my for loop did not work.)

Key Takeaways:

• Java is very similar to JavaScript (crazy, I know)
• Arrays are FIXED IN SIZE
  • You must define size and data type when creating an array
  • Example:

      int[] arrayName = new int[length]
    

    • int[] = list of integers
    • arrayName = name of the array
    • new int[length] = creates a new integer array of a length (replace length with an integer)
• Creating objects in Java:
  • Keywords: Come before defining things
    • public = can be accessed from anywhere in the code, similar to var
    • private = only accessible within the declared class, similar to let, incompatible with static
    • static = used to define methods that can be used by all instances of an object
    • void = used in place of return value type to indicate no return
  • Parameters:
    • Define parameter type and name for access
      • int, String, char, float, boolean