src/doc/book/second-edition/src/ch08-00-common-collections.md

   1 # Common Collections
   2
   3 Rust’s standard library includes a number of very useful data structures called
   4 *collections*. Most other data types represent one specific value, but
   5 collections can contain multiple values. Unlike the built-in array and tuple
   6 types, the data these collections point to is stored on the heap, which means
   7 the amount of data does not need to be known at compile time and can grow or
   8 shrink as the program runs. Each kind of collection has different capabilities
   9 and costs, and choosing an appropriate one for your current situation is a
  10 skill you’ll develop over time. In this chapter, we’ll discuss three
  11 collections that are used very often in Rust programs:
  12
  13 * A *vector* allows us to store a variable number of values next to each other.
  14 * A *string* is a collection of characters. We’ve discussed the `String` type
  15   previously, but in this chapter we’ll talk about it in depth.
  16 * A *hash map* allows us to associate a value with a particular key. It’s a
  17   particular implementation of the more general data structure called a *map*.
  18
  19 To learn about the other kinds of collections provided by the standard library,
  20 see [the documentation][collections].
  21
  22 [collections]: ../../std/collections/index.html
  23
  24 We’ll discuss how to create and update vectors, strings, and hash maps, as well
  25 as what makes each special.