Java Language - 10 - Strings and String Manipulation

Java Fundamentals – Strings and String Manipulation

Introduction

Strings are a fundamental data type in Java, used for representing text. String manipulation is a common task in Java programming and is crucial for tasks such as data parsing, text processing, and more. In this guide, we’ll explore the use of strings in Java and various string manipulation techniques.

Creating Strings

In Java, you can create strings using the String class. There are multiple ways to create strings, including:


String greeting = "Hello, world!";
String name = new String("Alice");

In the first example, we create a string using a string literal. In the second example, we use the String class constructor.

String Concatenation

String concatenation is the process of combining two or more strings into a single string. You can use the ‘+’ operator to concatenate strings:


String firstName = "John";
String lastName = "Doe";
String fullName = firstName + " " + lastName;

The ‘fullName’ string now contains “John Doe.”

String Length

You can find the length (the number of characters) of a string using the ‘length()’ method:


String text = "Java is fun!";
int length = text.length(); // 'length' is now 12

String Comparison

To compare two strings for equality, use the ‘equals()’ method. For case-insensitive comparison, use ‘equalsIgnoreCase()’:


String str1 = "apple";
String str2 = "Apple";
boolean isEqual = str1.equals(str2); // 'isEqual' is false
boolean isCaseInsensitiveEqual = str1.equalsIgnoreCase(str2); // 'isCaseInsensitiveEqual' is true

Substring Extraction

You can extract a substring from a string using the ‘substring()’ method. Provide the starting index and, optionally, the ending index:


String text = "Java Programming";
String sub = text.substring(5); // 'sub' is "Programming"
String sub2 = text.substring(0, 4); // 'sub2' is "Java"

String Searching

To find the position of a substring within a string, use the ‘indexOf()’ method. It returns the index of the first occurrence or -1 if not found:


String text = "The quick brown fox";
int position = text.indexOf("brown"); // 'position' is 10

String Modification

Strings are immutable in Java, meaning you cannot change their contents. To modify a string, you create a new one. Common string modification methods include ‘replace()’, ‘toUpperCase()’, and ‘toLowerCase()’:


String text = "Hello, World!";
String modified = text.replace("World", "Java"); // 'modified' is "Hello, Java!"
String upperCase = text.toUpperCase(); // 'upperCase' is "HELLO, WORLD!"
String lowerCase = text.toLowerCase(); // 'lowerCase' is "hello, world!"

String Splitting

You can split a string into an array of substrings using the ‘split()’ method. It’s useful for breaking down data into manageable pieces:


String data = "Alice,Bob,Charlie";
String[] names = data.split(",");
// 'names' is now an array containing {"Alice", "Bob", "Charlie"}

Conclusion

Strings and string manipulation are fundamental aspects of Java programming. Understanding how to create, modify, and work with strings is essential for various tasks, including text processing, data parsing, and building user-friendly applications.

Java Language – 10 – Strings and String Manipulation