Question

Write an application that uses String method compareTo to compare two strings input by the user. Output whether the first string is less than, equal to or greater than the second.

Short answer

Use `compareTo` to determine order, then print the appropriate comparison result.

Step-by-step solution

Understand the Problem

We need to compare two strings using the `compareTo` method in Java. This method will determine the lexicographical order of the strings, telling us if the first string is less than, equal to, or greater than the second string.

Gather Input

Prompt the user to input two strings. Use a Scanner class in Java to read these inputs. Suppose the strings are stored in variables `string1` and `string2`.

Utilize the compareTo Method

Call the `compareTo` method on the first string variable, passing the second string as an argument. The method signature looks like: `int result = string1.compareTo(string2);`. This will return an integer value: - A negative number if `string1` is lexicographically less than `string2`. - Zero if they are equal. - A positive number if `string1` is greater than `string2`.

Interpret and Display the Result

Using conditional statements, check the integer returned by `compareTo` and print the appropriate message: - If `result` is less than 0, print `"First string is less than second string."` - If `result` is equal to 0, print `"Both strings are equal."` - If `result` is greater than 0, print `"First string is greater than second string."`

Key concepts

Understanding the CompareTo Method

The `compareTo` method is a built-in method in Java that allows you to compare two strings lexicographically. This means it compares each character of the two strings based on their Unicode values as if ordered in a dictionary. By using `compareTo`, you can easily determine the order between two strings.

Here's how this method works:

• The method is invoked on one string and it takes another string as an argument.
• It returns an integer: a negative integer, zero, or a positive integer.
• If the first string comes before the second in lexicographical order, it returns a negative value.
• If both strings are identical, it returns zero.
• If the first string follows the second string, it returns a positive number.

These return values help decide the relative order of the strings. For instance, if you had the strings "apple" and "banana", calling `"apple".compareTo("banana")` would result in a negative number, indicating that "apple" comes before "banana".

What is Lexicographical Order?

Lexicographical order is a way of ordering words based on dictionary order, much like words are arranged in a dictionary. Each character has a corresponding Unicode value, and this numerical value is used to determine the order. It’s similar to alphabetical order, but because of the Unicode sorting system, uppercase and lowercase letters, as well as special characters, factor into the sequence.

When comparing strings:

• Lowercase letters have higher Unicode values than uppercase ones, meaning 'a' comes after 'Z'.
• Characters are considered one by one from the beginning until a difference is found.
• If two strings have the same beginning but differ later, the string with additional characters will be considered greater.

Understanding lexicographical order is crucial when you work with `compareTo` because that method uses this order to assess the positioning of one string relative to another.

Using the Scanner Class in Java

The `Scanner` class in Java is a convenient way to read user input from the console. It is widely used when working on console-based applications, allowing developers to capture and use user input effectively. Here’s a simple breakdown of how the `Scanner` class functions:

• You need to import the `java.util.Scanner` package to use it.
• Create an instance of `Scanner` to read input, often using `System.in` as the source to capture what the user types.
• Use methods like `nextLine()` to read entire lines of input as strings.
• Don’t forget to close the `Scanner` object after it’s used by calling the `close()` method. This helps to prevent resource leaks.

For example, to read two strings from the user, you'd set up a `Scanner` instance and use `nextLine()` to grab each string. This input can then be directly compared using the `compareTo` method for desired results.