Java String Methods
Built-in methods for manipulating text in Java
📝 What are String Methods?
String methods are built-in functions that help you manipulate text in Java. They let you change, search, and format strings easily without writing complex code yourself.
// Basic string methods example
String text = "Hello World";
System.out.println(text.length()); // 11
System.out.println(text.toUpperCase()); // HELLO WORLD
System.out.println(text.charAt(0)); // H
Types of String Methods
Length & Size
Get information about string size
Search & Find
Find characters and substrings
Cut & Extract
Get parts of strings
Transform
Change string format and case
🔹 Basic String Information
Get basic information about your strings:
public class StringInfo {
public static void main(String[] args) {
String name = "Java Programming";
// Get string length
System.out.println("Length: " + name.length());
// Check if empty
String empty = "";
System.out.println("Is empty: " + empty.isEmpty());
// Get character at position
System.out.println("First char: " + name.charAt(0));
System.out.println("Last char: " + name.charAt(name.length() - 1));
}
}Output:
Length: 16
Is empty: true
First char: J
Last char: g
🔹 Searching in Strings
Find text within strings:
public class StringSearch {
public static void main(String[] args) {
String sentence = "I love Java programming";
// Check if contains text
System.out.println("Contains 'Java': " + sentence.contains("Java"));
// Find position of text
System.out.println("Position of 'Java': " + sentence.indexOf("Java"));
// Check start and end
System.out.println("Starts with 'I': " + sentence.startsWith("I"));
System.out.println("Ends with 'ing': " + sentence.endsWith("ing"));
}
}Output:
Contains 'Java': true
Position of 'Java': 7
Starts with 'I': true
Ends with 'ing': true
🔹 Extracting Parts of Strings
Get specific parts of your strings:
public class StringExtract {
public static void main(String[] args) {
String fullName = "John Smith";
// Get substring
String firstName = fullName.substring(0, 4);
String lastName = fullName.substring(5);
System.out.println("First name: " + firstName);
System.out.println("Last name: " + lastName);
// Split string
String[] parts = fullName.split(" ");
System.out.println("Parts: " + parts[0] + " and " + parts[1]);
}
}Output:
First name: John
Last name: Smith
Parts: John and Smith
🔹 Transforming Strings
Change the format and content of strings:
public class StringTransform {
public static void main(String[] args) {
String message = " Hello World ";
// Change case
System.out.println("Upper: " + message.toUpperCase());
System.out.println("Lower: " + message.toLowerCase());
// Remove spaces
System.out.println("Trimmed: '" + message.trim() + "'");
// Replace text
String newMessage = message.replace("World", "Java");
System.out.println("Replaced: " + newMessage);
}
}Output:
Upper: HELLO WORLD
Lower: hello world
Trimmed: 'Hello World'
Replaced: Hello Java
🔹 Practical String Methods
Real-world examples of string manipulation:
Common Use Cases:
- Email validation: Check if contains "@" symbol
- Name formatting: Capitalize first letters
- Data cleaning: Remove extra spaces
- Text processing: Split sentences into words
public class PracticalExample {
public static void main(String[] args) {
// Email validation
String email = "[email protected]";
if (email.contains("@") && email.contains(".")) {
System.out.println("Valid email format");
}
// Format name
String name = "john doe";
String[] words = name.split(" ");
String formatted = "";
for (String word : words) {
formatted += word.substring(0, 1).toUpperCase() +
word.substring(1).toLowerCase() + " ";
}
System.out.println("Formatted: " + formatted.trim());
}
}