Question

Write an application that inputs a telephone number as a string in the form (555) 555-5555. The application should use an object of class StringTokenizer to extract the area code as a token, the first three digits of the phone number as a token and the last four digits of the phone number as a token. The seven digits of the phone number should be concatenated into one string. Both the area code and the phone number should be printed. Remember that you will have to change delimiter characters during the tokenization process.

Short answer

Extract the area code and first three and last four digits, then concatenate the digits for the final phone number.

Step-by-step solution

Import the Necessary Classes

To begin, ensure you have the right imports. For this task, we need to import `java.util.StringTokenizer`. This class assists in breaking the string into tokens efficiently.

Read the Phone Number Input

Capture the phone number input as a string. For simplicity, let's assume the input is provided directly in the code or from the user via a scanner. Example: `String phoneNumber = "(555) 555-5555";`.

Extract the Area Code

Instantiate a `StringTokenizer` with `(` as the delimiter to start extracting tokens. Use it to extract the area code by calling `nextToken()`, then discard the closing parenthesis `)`. Example: `StringTokenizer token = new StringTokenizer(phoneNumber, "(");` followed by `String areaCode = token.nextToken();`.

Extract the First Three Digits

Modify the delimiter of the `StringTokenizer` to handle the space and dash ` -` after extracting the area code. Use `nextToken()` again to get the next part of the phone number. Example: `token = new StringTokenizer(token.nextToken(), " -");` and `String firstThree = token.nextToken();`

Extract the Last Four Digits

Continue using the modified delimiter setup. Obtain the last four digits of the phone number using `nextToken()`. Example: `String lastFour = token.nextToken();`.

Concatenate the Phone Number Digits

Join the first three digits and the last four digits into a single string to get the full number without delimiters. Example: `String fullNumber = firstThree + lastFour;`.

Output the Result

Print both the area code and the concatenated phone number string (seven digits). Example output will be: `System.out.println("Area Code: " + areaCode);` and `System.out.println("Phone Number: " + fullNumber);`.

Key concepts

Java programming

Java is a versatile, object-oriented programming language that offers a lot of power for developing a variety of applications, from web-based solutions to mobile apps. It is known for its platform independence, which means that programs written in Java can run on any operating system that supports Java without the need for modification. This platform independence is achieved through the use of the Java Virtual Machine (JVM), which translates Java code into machine code that any computer can execute.

Java is also widely embraced because of its rich library ecosystem, which allows developers to implement advanced functionalities with relative ease. In the context of handling strings and tokenization, Java provides several in-built classes and methods that simplify the task of manipulating strings. One such class is the `StringTokenizer`, which is part of the `java.util` package and helps in parsing strings into meaningful components, often called tokens.

Understanding the basics of Java programming opens many doors when it comes to software development. It gives you the skills needed to work efficiently with data and create robust applications that perform various tasks, like parsing complex data entries such as phone numbers.

tokenization

Tokenization is a process in Java programming where you break a string into smaller elements called tokens. These tokens are useful for string analysis and manipulation. For example, in a phone number, the area code might be the first token, followed by the first three digits, and then the last four digits.

This concept is crucial in applications where input strings need to be parsed or processed. Java's `StringTokenizer` class is a tool for this purpose, allowing structured yet flexible extraction of data from strings.

Tokenization involves specifying a delimiter – a character or sequence of characters that separate tokens in the original string. For our phone number example, the delimiters would include parentheses `()`, space, and dash `-`. By defining these delimiters, the `StringTokenizer` class efficiently isolates each segment of the phone number.

Key uses of tokenization include:

• Data parsing: Reflects the way data becomes understandable, like breaking down an address into street, city, state, etc.
• Input validation: Helps analyze parts of a string to enforce data rules.
• Algorithm preparation: Gets data ready and in the right format for computational analysis.

Tokenization is essential for string manipulation tasks and enhances data processing capabilities in Java applications.

string manipulation

In Java programming, string manipulation refers to various operations you can perform on strings to alter or utilize them. Whether it's extracting segments, changing their format, or analyzing their content, these operations are fundamental in the creation of many Java-based applications.

Key operations include:

• Extracting substrings: Using methods like `substring()` to retrieve parts of a string.
• Concatenating strings: Joining multiple strings or string segments using the `+` operator or the `concat()` method.
• Replacing characters: Utilizing functions like `replace()` to change specific parts of a string.
• Changing case: Transforming a string to uppercase or lowercase for uniformity or comparison purposes.

Java offers efficient mechanisms for string manipulation through its robust utilities available in the `String` class and related libraries, such as `StringTokenizer`. These utilities allow developers to convert input strings into desired formats, extract necessary parts, and prepare data for further processing.

Manipulating strings with precision allows Java programs to respond to various input formats, enhancing their flexibility and usability. From parsing data inputs to displaying formatted outputs, string manipulation is an integral skill in an effective programming toolkit.

Java String class

The Java `String` class is one of the most used classes in Java programming due to its role in handling text data. A `String` in Java is an object that represents a sequence of characters. Strings are immutable, meaning once a string is created, it cannot be altered. However, while the string's value cannot change, new strings can be derived from existing ones using various methods.

Key features and methods of the `String` class include:

• Immutability: Provides security and efficiency, ensuring that string data remain unchanged, preventing unwanted alterations.
• Common methods: The `String` class offers a wealth of methods like `length()`, `charAt()`, `substring()`, `indexOf()`, `toLowerCase()`, and `toUpperCase()`, each facilitating different tasks like measuring string length, accessing characters, and formatting.
• String concatenation: Allows easy joining of strings through the `+` operator or `concat()` method, enabling the construction of meaningful text components.

The relationship between the `String` class and utilities like `StringTokenizer` is evident in activities like tokenization, where complex string manipulation is required. The immutable nature ensures that baseline data remains unchanged while offering various utilities to derive new, manipulated string data. Understanding the `String` class and its capabilities forms the backbone of mastering string operations in Java.