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Trail: Learning the Java Language
Lesson: Language Basics

## Answers to Questions and Exercises: Control Flow

### Answers to Questions

> 1. Question: Look at the `SortDemo` program. What control flow statements does it contain?
>    Answer: `SortDemo` contains four control statements. In order: two `for` statements, an `if` statement, and another `for` statement.
> 2. Question: What's wrong with the following code snippet:

>    >     if (i = 1) {
>    >         /* do something */
>    >     }

>    Answer: It should use `==` instead of `=`. If you try to compile the preceding code, the compiler warns you that a `boolean` value is required instead of an `int` value.
> 3. Question: Look at the `WhileDemo` program and the `DoWhileDemo` program. What would the output be from each program if you changed the value of each program's `copyFromMe` string to `golly gee. this is fun.` Explain why you think each program will have the predicted output.
>    Answer: `NewWhileDemo` and `NewDoWhileDemo`. The modified `WhileDemo` displays a blank line because the first letter is a `g`, and thus the loop is not entered and no characters are appended to `copyToMe`. The modified `DoWhileDemo` displays `golly` because the first `g` is ignored, and the second one terminates the loop without adding the second `g` to the string.

### Exercises

> 1. Consider the following code snippet.

>    >     if (aNumber >= 0)
>    >         if (aNumber == 0) System.out.println("first string");
>    >     else System.out.println("second string");
>    >     System.out.println("third string");

>    1. Exercise: What output do you think the code will produce if `aNumber` is 3?
>       Solution:

>       >     second string
>       >     third string

>    2. Exercise: Write a test program containing the code snippet; make `aNumber` 3. What is the output of the program? Is it what you predicted? Explain why the output is what it is. In other words, what is the control flow for the code snippet?
>       Solution: `NestedIf`

>       >     second string
>       >     third string

>       3 is greater than or equal to 0, so execution progresses to the second `if` statement. The second `if` statement's test fails because 3 is not equal to 0. Thus, the `else` clause executes (since it's attached to the second `if` statement). Thus, `second string` is displayed. The final `println` is completely outside of any `if` statement, so it always gets executed, and thus `third string` is always displayed.
>    3. Exercise: Using only spaces and line breaks, reformat the code snippet to make the control flow easier to understand.
>       Solution:

>       >     if (aNumber >= 0)
>       >         if (aNumber == 0)
>       >             System.out.println("first string");
>       >         else
>       >             System.out.println("second string");

>       >     System.out.println("third string");

>    4. Exercise: Use braces `{` and `}` to further clarify the code and reduce the possibility of errors by future maintainers of the code.
>       Solution: Adhering to the Sun code conventions:

>       >     if (aNumber >= 0) {
>       >         if (aNumber == 0) {
>       >             System.out.println("first string");
>       >         } else {
>       >             System.out.println("second string");
>       >         }
>       >     }

>       >     System.out.println("third string");

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