基本字符串操作

fn main() {
    // Statically allocated string slice
    let hello = "Hello world";

    // This is equivalent to the previous one
    let hello_again: &'static str = "Hello world";

    // An empty String
    let mut string = String::new();

    // An empty String with a pre-allocated initial buffer
    let mut capacity = String::with_capacity(10);

    // Add a string slice to a String
    string.push_str("foo");

    // From a string slice to a String
    // Note: Prior to Rust 1.9.0 the to_owned method was faster
    // than to_string. Nowadays, they are equivalent.      
    let bar = "foo".to_owned();
    let qux = "foo".to_string();

    // The String::from method is another way to convert a
    // string slice to an owned String.
    let baz = String::from("foo");

    // Coerce a String into &str with &
    let baz: &str = &bar;
}

注意： String::new 和 String::with_capacity 方法都将创建空字符串。但是，后者分配初始缓冲区，使其最初变慢，但有助于减少后续分配。如果已知 String 的最终大小，则首选 String::with_capacity。