Uppercase and Lowercase in Rust in Rust

In Rust, you can convert a string to uppercase or lowercase using the built-in .to_uppercase() and .to_lowercase() methods:

let s = "Hello World";

let upper = s.to_uppercase();
// upper == "HELLO WORLD"

let lower = s.to_lowercase();
// lower == "hello world"

.to_uppercase() converts every character to its uppercase form, and .to_lowercase() converts every character to its lowercase form. Both methods return a new String and do not modify the original.