The extra line:

str = scan.nextLine();

is used to consume the leftover newline character in the input buffer before reading the actual string input.

Why is this necessary?

• When you use scan.nextInt() and scan.nextDouble(), they only read the number and do not consume the newline character (\n) that is entered after the number.
• This means that after reading the integer and double, the buffer still contains the newline character from when the user pressed Enter.
• If you directly call scan.nextLine(), it will read this leftover newline instead of the actual string input.

How does this extra scan.nextLine(); fix the issue?

• The first scan.nextLine(); consumes the leftover newline from nextDouble(), effectively clearing the buffer.
• The second scan.nextLine(); then reads the actual string input.

Example Input & Behavior

Input:

5
3.14
Hello World

Expected Output:

String: Hello World
Double: 3.14
Int: 5

Actual Output:

String:  (empty)
Double: 3.14
Int: 5

Why? - nextInt() reads 5, but \n remains in the buffer. - nextDouble() reads 3.14, but \n remains in the buffer. - nextLine() immediately reads this leftover \n, returning an empty string instead of "Hello World".

Input:

5
3.14
Hello World

Output:

String: Hello World
Double: 3.14
Int: 5

Why? - First nextLine(); clears the leftover newline. - Second nextLine(); correctly reads "Hello World".

Alternative Approach

Instead of:

String str = scan.nextLine();
str = scan.nextLine();

You can write:

scan.nextLine(); // Consume the leftover newline
String str = scan.nextLine(); // Read the actual input

This makes the intent clearer.

Final Answer:

The extra scan.nextLine(); is used to consume the leftover newline character after reading the integer and double, ensuring that the next nextLine() correctly reads the user’s input.