Java
String name = "Sita Karki";
System.out.println(name.length()); // 10
System.out.println(name.toUpperCase()); // SITA KARKI
System.out.println(name.toLowerCase());
System.out.println(name.charAt(0)); // S
System.out.println(name.indexOf("Karki")); // 5, or -1 if absent
System.out.println(name.substring(0, 4)); // Sita
System.out.println(name.replace("Sita", "Gita"));
System.out.println(name.trim()); // remove leading/trailing spaces
System.out.println(name.contains("Karki")); // true
System.out.println(name.isEmpty()); // false
System.out.println(name.isBlank()); // false (Java 11+)Comparing
Java
String a = "hello";
String b = "HELLO";
a.equals(b); // false
a.equalsIgnoreCase(b); // true
a.compareTo(b); // >0, 0, or <0 — for sortingSplitting and joining
Java
String csv = "ram,shyam,hari";
String[] parts = csv.split(",");
String joined = String.join(" | ", parts); // "ram | shyam | hari"Strings are immutable
Every "modification" creates a new String; the original never changes.
Java
String s = "hello";
s.toUpperCase(); // result thrown away!
System.out.println(s); // still "hello"
s = s.toUpperCase(); // correct — reassign
System.out.println(s); // "HELLO"StringBuilder for loops
Because of immutability, building a string with += inside a loop
creates a new object every iteration — quadratic time. Use
StringBuilder:
Java
StringBuilder sb = new StringBuilder();
for (int i = 0; i < 1000; i++) {
sb.append(i).append(",");
}
String result = sb.toString();Formatting
Java
String s = String.format("Name: %s, Total: NPR %.2f", "Sita", 1250.5);
System.out.println(s);Text blocks (Java 15+)
Multi-line strings without escaping:
Java
String json = """
{
"name": "Sita",
"city": "Kathmandu"
}
""";