1 // Start with a penny 2 |/ double it every day 3 // how much do you have in a 30-day month? 4 public class DebugSix1 5 { public static void main(String args[]) 8. final int DAYS = 30; 9. double money 0.01; 10 double moneyAmt = 2 * money; 11 for(int x = 2; x <= DAYS; x++){ 12 System.out.println("After day " + x + " you have + moneyAmt); 13 } 14 15 }

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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Start with a penny, double it every day. How much do you have in a 30-day month?

***How do I fix my code? I want the output to look the expected output in red.***

### Java Code: Doubling a Penny

This code aims to simulate the process of starting with a penny and doubling its value every day for a 30-day month. The logic is implemented in a simple Java program.

#### Code Explanation

```java
// Start with a penny
// double it every day
// how much do you have in a 30-day month?
public class DebugSix1
{
    public static void main(String args[])
    {
        final int DAYS = 30;
        double money = 0.01;
        double moneyAmt = 2 * money;
        for(int x = 2; x <= DAYS; x++)
        {
            System.out.println("After day " + x + " you have " + moneyAmt);
        }
    }
}
```

1. **Start with a Penny**: The variable `money` is initialized to 0.01, representing the initial amount.
   
2. **Calculating Amount**: The variable `moneyAmt` is meant to double the initial amount (`money`) every day.

3. **Loop through Each Day**: 
   - A `for` loop starts from day 2 up to 30.
   - It prints the message "After day x you have y" indicating the amount after each day.
   - There seems to be a logical error since `moneyAmt` is not updated within the loop, leading to incorrect output.

#### Output Analysis

- The output column in the terminal shows the series of printed statements, but all values remain at 0.02, indicating no actual doubling is occurring. This is due to `moneyAmt` not being recalculated for each iteration.

#### Corrective Action

To implement the intended doubling, `moneyAmt` should be updated inside the loop:

```java
for(int x = 2; x <= DAYS; x++)
{
    moneyAmt *= 2; // Correctly doubles the amount
    System.out.println("After day " + x + " you have " + moneyAmt);
}
```

### Key Takeaways

- Ensure variables intended to update are manipulated inside the loop.
- Properly test and debug code to achieve expected results.
- Understanding the logic flow in loops is essential for programming tasks such as financial computations.
Transcribed Image Text:### Java Code: Doubling a Penny This code aims to simulate the process of starting with a penny and doubling its value every day for a 30-day month. The logic is implemented in a simple Java program. #### Code Explanation ```java // Start with a penny // double it every day // how much do you have in a 30-day month? public class DebugSix1 { public static void main(String args[]) { final int DAYS = 30; double money = 0.01; double moneyAmt = 2 * money; for(int x = 2; x <= DAYS; x++) { System.out.println("After day " + x + " you have " + moneyAmt); } } } ``` 1. **Start with a Penny**: The variable `money` is initialized to 0.01, representing the initial amount. 2. **Calculating Amount**: The variable `moneyAmt` is meant to double the initial amount (`money`) every day. 3. **Loop through Each Day**: - A `for` loop starts from day 2 up to 30. - It prints the message "After day x you have y" indicating the amount after each day. - There seems to be a logical error since `moneyAmt` is not updated within the loop, leading to incorrect output. #### Output Analysis - The output column in the terminal shows the series of printed statements, but all values remain at 0.02, indicating no actual doubling is occurring. This is due to `moneyAmt` not being recalculated for each iteration. #### Corrective Action To implement the intended doubling, `moneyAmt` should be updated inside the loop: ```java for(int x = 2; x <= DAYS; x++) { moneyAmt *= 2; // Correctly doubles the amount System.out.println("After day " + x + " you have " + moneyAmt); } ``` ### Key Takeaways - Ensure variables intended to update are manipulated inside the loop. - Properly test and debug code to achieve expected results. - Understanding the logic flow in loops is essential for programming tasks such as financial computations.
**Results Explanation:**

The results display a pattern of exponential growth over a period of 30 days. The value approximately doubles each day, illustrating how quickly exponential growth can increase a quantity over time. This is a common mathematical concept used in various fields such as finance, biology, and computer science.

Here is the detailed transcription of the daily growth:

- After day 2 you have 0.02
- After day 3 you have 0.04
- After day 4 you have 0.08
- After day 5 you have 0.16
- After day 6 you have 0.32
- After day 7 you have 0.64
- After day 8 you have 1.28
- After day 9 you have 2.56
- After day 10 you have 5.12
- After day 11 you have 10.24
- After day 12 you have 20.48
- After day 13 you have 40.96
- After day 14 you have 81.92
- After day 15 you have 163.84
- After day 16 you have 327.68
- After day 17 you have 655.36
- After day 18 you have 1310.72
- After day 19 you have 2621.44
- After day 20 you have 5242.88
- After day 21 you have 10485.76
- After day 22 you have 20971.52
- After day 23 you have 41943.04
- After day 24 you have 83886.08
- After day 25 you have 167772.16
- After day 26 you have 335544.32
- After day 27 you have 671088.64
- After day 28 you have 1342177.28
- After day 29 you have 2684354.56
- After day 30 you have 5368709.12

These numbers illustrate the rapid increase due to exponential growth. Initially, increases are small, but eventually, they become extremely large. This example is often used to demonstrate concepts like compound interest and population growth.
Transcribed Image Text:**Results Explanation:** The results display a pattern of exponential growth over a period of 30 days. The value approximately doubles each day, illustrating how quickly exponential growth can increase a quantity over time. This is a common mathematical concept used in various fields such as finance, biology, and computer science. Here is the detailed transcription of the daily growth: - After day 2 you have 0.02 - After day 3 you have 0.04 - After day 4 you have 0.08 - After day 5 you have 0.16 - After day 6 you have 0.32 - After day 7 you have 0.64 - After day 8 you have 1.28 - After day 9 you have 2.56 - After day 10 you have 5.12 - After day 11 you have 10.24 - After day 12 you have 20.48 - After day 13 you have 40.96 - After day 14 you have 81.92 - After day 15 you have 163.84 - After day 16 you have 327.68 - After day 17 you have 655.36 - After day 18 you have 1310.72 - After day 19 you have 2621.44 - After day 20 you have 5242.88 - After day 21 you have 10485.76 - After day 22 you have 20971.52 - After day 23 you have 41943.04 - After day 24 you have 83886.08 - After day 25 you have 167772.16 - After day 26 you have 335544.32 - After day 27 you have 671088.64 - After day 28 you have 1342177.28 - After day 29 you have 2684354.56 - After day 30 you have 5368709.12 These numbers illustrate the rapid increase due to exponential growth. Initially, increases are small, but eventually, they become extremely large. This example is often used to demonstrate concepts like compound interest and population growth.
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