How can you comment a single line in Java?

A single line comment in Java is created using "//". This syntax allows developers to write notes or explanations in the code that are not executed by the compiler, making it easier to understand the code's functionality and intentions. The "//" indicates that everything following it on that line is a comment and will be ignored by the Java compiler during the execution of the program.

Using this commenting method is particularly useful for brief comments, such as marking what a specific line of code does, or temporarily disabling a part of the code by commenting it out. This practice helps maintain readability and provides context for others (or yourself) when revisiting the code later.

In contrast, the other options represent methods that are either incorrect or do not conform to Java's commenting standards. For instance, the "#" symbol is commonly used in languages like Python for comments but is not valid in Java. The "/* comment */" notation is used for multi-line comments, which shows that it is not suitable for single-line contexts. Lastly, using "" does not provide a valid commenting option in Java, as it represents an empty string rather than a comment.