String Methods

1// Information methods
2String str = "  Hello World  ";
3
4str.length();           // 15 (includes spaces)
5str.isEmpty();          // false
6str.isBlank();          // false (Java 11+)
7"".isEmpty();           // true
8"   ".isBlank();        // true (Java 11+)
9
10// Access methods
11str.charAt(2);          // 'H' (after spaces)
12str.substring(2, 7);    // "Hello"
13str.substring(8);       // "World  "
14str.toCharArray();      // char[] {'H', 'e', 'l', 'l', 'o', ...}
15
16// Search methods
17str.indexOf('o');       // 6 (first occurrence)
18str.indexOf('o', 7);    // 9 (search from index 7)
19str.lastIndexOf('o');   // 9
20str.indexOf("World");   // 8
21str.contains("World");  // true
22str.startsWith("  H");  // true
23str.endsWith("  ");     // true

1// Transformation methods
2String str = "  Hello World  ";
3
4str.toUpperCase();      // "  HELLO WORLD  "
5str.toLowerCase();      // "  hello world  "
6
7// Trimming whitespace
8str.trim();             // "Hello World" (removes leading/trailing)
9str.strip();            // "Hello World" (Java 11+, Unicode aware)
10str.stripLeading();     // "Hello World  " (Java 11+)
11str.stripTrailing();    // "  Hello World" (Java 11+)
12
13// Replace methods
14String text = "Hello, Hello!";
15text.replace('H', 'J');            // "Jello, Jello!"
16text.replace("Hello", "Hi");       // "Hi, Hi!"
17text.replaceFirst("Hello", "Hi");  // "Hi, Hello!"
18text.replaceAll("[aeiou]", "*");   // "H*ll*, H*ll*!" (regex)
19
20// Repeat (Java 11+)
21"Ha".repeat(3);         // "HaHaHa"

1// Split and Join
2String csv = "apple,banana,cherry";
3
4// Split into array
5String[] fruits = csv.split(",");
6// ["apple", "banana", "cherry"]
7
8// Split with limit
9"a:b:c:d".split(":", 2);  // ["a", "b:c:d"]
10
11// Join array into string
12String joined = String.join(", ", fruits);
13// "apple, banana, cherry"
14
15// Join with stream
16String fromList = String.join("-", Arrays.asList("A", "B", "C"));
17// "A-B-C"
18
19// Format methods
20String.format("Name: %s, Age: %d", "Alice", 25);
21// "Name: Alice, Age: 25"
22
23String.format("Price: $%.2f", 19.99);
24// "Price: $19.99"
25
26// Formatted (Java 15+)
27"Hello %s!".formatted("World");
28// "Hello World!"

1// Java 11+ String methods
2String text = "  Java Programming  ";
3
4// strip() is Unicode-aware (better than trim())
5text.strip();           // "Java Programming"
6
7// Check if blank
8"   \t\n".isBlank();    // true
9
10// Lines (splits by line terminators)
11String multiline = "Line1\nLine2\nLine3";
12multiline.lines().forEach(System.out::println);
13
14// Repeat
15"=".repeat(20);         // "===================="
16
17// Java 12+ methods
18String indented = "Hello".indent(4);  // "    Hello\n"
19
20// Transform (Java 12+)
21String result = "hello"
22    .transform(String::toUpperCase)
23    .transform(s -> s + "!");
24// "HELLO!"
25
26// Java 15+ methods
27String stripped = "  text  ".stripIndent();  // For text blocks