Strings and Functions

The String type

Unlike primitive types, String is an object that represents a sequence of characters.

Immutability

Strings in Java are immutable. If you change the value of a String, Java creates a new object in memory.

String greeting = "Hello";
greeting = greeting + " world"; // A new "Hello world" object is created

Useful String methods

• length(): Length of the text.
• toUpperCase() / toLowerCase(): Change to uppercase/lowercase.
• contains("text"): Checks whether it contains a word.
• indexOf("a"): Finds the position of a character.
• equals("other"): Compares contents (do not use ==!).

Functions (Methods)

A function is a reusable block of code that performs a specific task.

public static int sum(int a, int b) {
    return a + b;
}

// Call:
int result = sum(5, 3);

Structure of a function:

1. Return type: The data it returns (int, String, void if it returns nothing).
2. Name: To identify it.
3. Parameters: Data it receives to work with.
4. Body: The code inside { }.