• Develop code to represent branching logical processes by using selection statements and determine the result of these processes

Assignment

if statements and one-way selection

Selection is used to create branching execution, where some code will only run under certain conditions. Typically, this is done with if statements, which look like this:

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if (boolean expression) {
   Do Statement1;
   Do Statement2;
   ...
   Do StatementN;
}

If the boolean expression evaluates to true, then all the statements in the block execute from top to bottom. Blocks of code are marked by braces { }, which you’ve seen when defining methods and classes.

CSAwesome2 likes to put their opening brace on the next line, while I and most of the planet prefer the same line. We do this because there’s more of a premium on vertical space than horizontal (and my formatter has that as the default).

Also, if there is only one statement in the block, you can get away with omitting braces altogether. I don’t recommend that since it can lead to code readability issues. I won’t show it here, but you’ll see it in the book.

If the boolean expression evaluates to false, the entire block is skipped. This is useful for checking preconditions on a method. If they aren’t met, the logic can be skipped and the method can exit gracefully.

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public static String inverse(int n, int d) {
    if (n != 0) {
        return d + "/" + n;
    }   

    return "Cannot be inverted.";
}

Two-way selection

Having an alternate block of code execute can be helpful, so enter the else keyword. If the original boolean statement evaluates to false, then any code in the adjoining else block will run instead.

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if (boolean expression) {
   statement1;
   statement2;
} else {
   do other statement;
   and another one;
}

I can easily rewrite my method from earlier with an else block, which will also make it a bit easier to read (debatable).

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public static String inverse(int n, int d) {
    if (n != 0) {
        return d + "/" + n;
    } else {
        return "Cannot be inverted.";
    }
}

Writing the boolean expressions will likely be your biggest hurdle. The logical statements will either be difficult to turn into code, or the code itself will be hard to parse.