Strings in Java with Examples
This article dives into the essential concepts and functionalities related to strings in the Java programming language. Strings play a pivotal role in programming, serving as objects designed to hold sequences of character values.
This article explores the creation, manipulation, and storage of strings in Java, covering both literal and dynamic allocation methods. Additionally, we will also be covering key classes and interfaces associated with strings, shedding light on their roles in handling textual data.
The discussion includes practical examples and insights into memory allocation optimization, making it a comprehensive guide for developers working with strings in Java.
What is a String in Java?
Strings in Java are objects designed to hold sequences of character values. Each character is stored using a 16-bit encoding known as UTF-16. In Java, a string functions similarly to an array of characters. Strings in Java are typically used to represent and manipulate textual information.
Strings can include letters, numbers, symbols, and whitespace. Strings play a fundamental role in various programming tasks, from simple output and user input to more complex text processing and data manipulation.
Below is an example of a string in Java:
String greeting = "Welcome to FirstCode!";
The string literal “Welcome to FirstCode!” in this example is allocated to the welcome variable. You can think of a string as a series of characters arranged in a specific order.
What are strings used for?
Strings can be used for a wide range of purposes, including:
1. Output and Display: Printing messages to the console or displaying information to users often involves the use of strings.
2. User Input: Reading and processing user input from the keyboard often involves strings.
3. Text Processing: Manipulating and processing textual data, such as searching for substrings, extracting information, or modifying content.
4. Data Representation: Storing and representing data in a human-readable format, such as configuration files, XML, or JSON.
Creating a String in Java
In Java, the creation of strings can be accomplished through two different methods:
String Literal:
The most common and concise way to create a string in Java is by using string literals. A string literal is a sequence of characters enclosed within double quotation marks. When a string literal is assigned to a variable, Java automatically checks the string pool to see if an identical string already exists. If found, the variable is assigned a reference to the existing string; otherwise, a new string is created in the pool.
Example:
String s = "FirstCode";
In this example, the string “FirstCode” is a literal, and the variable s holds a reference to it.
Using the new Keyword:
Another way to create a string in Java is by explicitly using the new keyword along with the String class constructor. This method creates a new instance of the String class, regardless of whether an identical string already exists in the string pool. This approach is less common than using string literals but can be useful in scenarios where dynamic string creation or manipulation is required.
Example:
String s = new String("FirstCode");
The new keyword is used to create a new String object with the content “FirstCode”.
How are strings stored in Java?
When a String object is created as a literal, it is stored in the String constant pool, allowing the Java Virtual Machine (JVM) to optimize the initialization of String literals for improved performance. However, if a string is declared using the new operator, indicating dynamic allocation, it is assigned a new memory location in the heap.
Strings created this way are not added to the String constant pool. To store a dynamically allocated string in the constant pool, the intern() method can be used. It is generally recommended to use String literals because it enables the JVM to optimize memory allocation. This optimization becomes particularly significant when dealing with a large number of String objects.
Classes and interfaces related to strings in Java.
In Java, there are interfaces and classes associated with handling strings, let us take a look at them, and see what they have to offer:
CharBuffer:
The CharBuffer class implements the CharSequence interface in Java. Its purpose is to enable the use of character buffers as substitutes for CharSequences. An example of its application can be found in the java.util.regex package, particularly in regular expressions.
String:
In Java, a string is a group of characters. It’s essential to understand that objects of the String class are immutable, meaning they remain constant and cannot be modified once created.
CharSequence Interface:
The CharSequence Interface is employed for representing character sequences in Java. Classes that implement this interface provide a range of functionalities, including substring operations, locating the last and first occurrences, concatenation, and case transformations (toUpper and toLower). Let us take a look at the 3 classes that implement this interface:
a. String Class in Java: The String class in Java is characterized by immutability, signifying its constancy once created. Any desire to modify it necessitates the creation of a new object. Even the operations it offers, such as toupper and tolower, generate a new object rather than modifying the original one. Importantly, it inherently ensures thread safety.
Immutability provides several advantages, including thread safety. Since Strings cannot be changed, they can be safely shared among multiple threads without the risk of unexpected modifications. This inherent thread safety makes String objects a reliable choice for scenarios involving concurrent access. The syntax to initialize a string using the string class is shown below:
String str = new String("FirstCode");
b. String Buffer: StringBuffer stands as a counterpart to the String class, offering extensive functionality akin to manipulating strings. While strings denote fixed-length and immutable character sequences, StringBuffer represents dynamic and modifiable character sequences. Unlike String, StringBuffer is mutable and is designed to be thread-safe.
This attribute makes it suitable for scenarios where multiple threads need to access a shared object of StringBuffer in a multi-threaded environment. However, it’s crucial to acknowledge that this thread safety comes with additional overhead, making StringBuffer preferable for situations involving concurrent program execution. The syntax to initialize a string using the string buffer class is shown below:
StringBuffer demoString = new StringBuffer("FirstCode");
c. String builder: In Java, StringBuilder serves as a dynamic and alterable sequence of characters, offering a mutable counterpart to the immutable nature of the String class. Unlike String, which creates an unchangeable sequence of characters, StringBuilder allows modifications to the character sequence.
Notably, StringBuilder is not designed to be thread-safe, making it suitable for scenarios involving single-threaded programs. Its usage is confined to within a single thread, eliminating any additional overhead associated with thread safety. The syntax to initialize a string using the string builder class is shown below:
StringBuilder str1= new StringBuilder();
str1.append("FirstCode");
String tokenization in Java
The StringTokenizer class in Java serves the purpose of dividing a string into tokens. This involves breaking the string into smaller units or segments. An instance of StringTokenizer maintains an internal position within the tokenized string, with certain operations advancing this position beyond processed characters.
The tokens are obtained by extracting substrings from the original string used to instantiate the StringTokenizer object. The syntax to use the tokenizer class in Java is shown below:
StringTokenizer tokenizer = new StringTokenizer(“Example string to tokenize”);
On the other hand, the StringJoiner class in the java.util package, is designed for constructing a sequence of characters or strings separated by a specified delimiter. Additionally, it allows for the inclusion of a provided prefix and suffix.
While similar functionality can be achieved using the StringBuilder class by appending a delimiter after each string, StringJoiner simplifies this process, requiring less code. The syntax to use the StringJoiner class in Java is shown below:
public StringJoiner(CharSequence delimiter)
Conclusion
In conclusion, understanding how to work with strings is super important for effective Java programming because strings are used everywhere to deal with text. We covered different ways to create strings, like using simple text or more complicated methods. We also talked about some special classes like CharBuffer, String, StringBuffer, and StringBuilder that help us handle strings in Java.
We also covered practical examples, like how to break a string into smaller parts using StringTokenizer and how to put strings together using StringJoiner. This makes it easier to see how all this info can be useful in real-life situations. With the knowledge shared here, Java developers can handle string-related tasks confidently and make their programs use memory more efficiently.