How to Peek at the Next Element in a Java Scanner?

How can I peek at the next element using a Java Scanner?

Scanner scanner = new Scanner(System.in);

if (scanner.hasNext()) {
    String nextElement = scanner.next();
    // You can process the nextElement here
} else {
    // Handle the case when no more elements are available
}

Peeking at the next element in a Java Scanner allows you to check what the next token will be without consuming it. This is useful for conditional logic based on user input or file parsing where you need to look ahead before making decisions.

Scanner scanner = new Scanner(System.in);

if (scanner.hasNext()) {
    String nextElement = scanner.next(); // Reads the next element
    // Process the nextElement according to your business logic
    System.out.println("Next Element: " + nextElement);
} else {
    System.out.println("No more elements are available.");
}

Causes

• The need to inspect the next input token before deciding how to handle it.
• Avoiding unnecessary processing if the next token does not meet certain criteria.

Solutions

• Using `hasNext()` method to check if there is another token available without consuming it.
• Utilize a temporary buffer to store the token if the Scanner's position needs to be reverted.

Mistake: Using next() without checking hasNext() could lead to NoSuchElementException.

Solution: Always check hasNext() before using next().