diff --git a/solutions/generics-traits/advanced-trait.md b/solutions/generics-traits/advanced-trait.md
new file mode 100644
index 0000000..22f2e14
--- /dev/null
+++ b/solutions/generics-traits/advanced-trait.md
@@ -0,0 +1,228 @@
+1.
+```rust
+struct Container(i32, i32);
+
+// A trait which checks if 2 items are stored inside of container.
+// Also retrieves first or last value.
+trait Contains {
+    // Define generic types here which methods will be able to utilize.
+    type A;
+    type B;
+
+    fn contains(&self, _: &Self::A, _: &Self::B) -> bool;
+    fn first(&self) -> i32;
+    fn last(&self) -> i32;
+}
+
+impl Contains for Container {
+    // Specify what types `A` and `B` are. If the `input` type
+    // is `Container(i32, i32)`, the `output` types are determined
+    // as `i32` and `i32`.
+    type A = i32;
+    type B = i32;
+
+    // `&Self::A` and `&Self::B` are also valid here.
+    fn contains(&self, number_1: &i32, number_2: &i32) -> bool {
+        (&self.0 == number_1) && (&self.1 == number_2)
+    }
+    // Grab the first number.
+    fn first(&self) -> i32 { self.0 }
+
+    // Grab the last number.
+    fn last(&self) -> i32 { self.1 }
+}
+
+fn difference<C: Contains>(container: &C) -> i32 {
+    container.last() - container.first()
+}
+
+fn main() {
+    let number_1 = 3;
+    let number_2 = 10;
+
+    let container = Container(number_1, number_2);
+
+    println!("Does container contain {} and {}: {}",
+        &number_1, &number_2,
+        container.contains(&number_1, &number_2));
+    println!("First number: {}", container.first());
+    println!("Last number: {}", container.last());
+    
+    println!("The difference is: {}", difference(&container));
+}
+```
+
+2.
+```rust
+impl<T: Sub<Output = T>> Sub<Point<T>> for Point<T> {
+    type Output = Self;
+
+    fn sub(self, other: Self) -> Self::Output {
+        Point {
+            x: self.x - other.x,
+            y: self.y - other.y,
+        }
+    }
+}
+```
+
+```rust
+impl<T: Sub<Output = T>> Sub<Self> for Point<T> {
+    type Output = Self;
+
+    fn sub(self, other: Self) -> Self::Output {
+        Point {
+            x: self.x - other.x,
+            y: self.y - other.y,
+        }
+    }
+}
+```
+
+```rust
+impl<T: Sub<Output = T>> Sub for Point<T> {
+    type Output = Self;
+
+    fn sub(self, other: Self) -> Self::Output {
+        Point {
+            x: self.x - other.x,
+            y: self.y - other.y,
+        }
+    }
+}
+```
+
+3.
+```rust
+trait Pilot {
+    fn fly(&self) -> String;
+}
+
+trait Wizard {
+    fn fly(&self) -> String;
+}
+
+struct Human;
+
+impl Pilot for Human {
+    fn fly(&self) -> String {
+        String::from("This is your captain speaking.")
+    }
+}
+
+impl Wizard for Human {
+    fn fly(&self) -> String {
+        String::from("Up!")
+    }
+}
+
+impl Human {
+    fn fly(&self) -> String {
+        String::from("*waving arms furiously*")
+    }
+}
+
+fn main() {
+    let person = Human;
+    assert_eq!(Pilot::fly(&person), "This is your captain speaking.");
+    assert_eq!(Wizard::fly(&person), "Up!");
+
+    assert_eq!(person.fly(), "*waving arms furiously*");
+
+    println!("Success!")
+}
+```
+
+4.
+```rust
+trait Person {
+    fn name(&self) -> String;
+}
+
+// Person is a supertrait of Student.
+// Implementing Student requires you to also impl Person.
+trait Student: Person {
+    fn university(&self) -> String;
+}
+
+trait Programmer {
+    fn fav_language(&self) -> String;
+}
+
+// CompSciStudent (computer science student) is a subtrait of both Programmer 
+// and Student. Implementing CompSciStudent requires you to impl both supertraits.
+trait CompSciStudent: Programmer + Student {
+    fn git_username(&self) -> String;
+}
+
+fn comp_sci_student_greeting(student: &dyn CompSciStudent) -> String {
+    format!(
+        "My name is {} and I attend {}. My favorite language is {}. My Git username is {}",
+        student.name(),
+        student.university(),
+        student.fav_language(),
+        student.git_username()
+    )
+}
+
+struct CSStudent {
+    name: String,
+    university: String,
+    fav_language: String,
+    git_username: String
+}
+
+impl Person for CSStudent {
+    fn name(&self) -> String {
+        self.name.clone()
+    }
+}
+
+impl Student for CSStudent {
+    fn university(&self) -> String {
+        self.university.clone()
+    }
+}
+
+impl Programmer for CSStudent {
+    fn fav_language(&self) -> String {
+        self.fav_language.clone()
+    }
+}
+
+impl CompSciStudent for CSStudent {
+    fn git_username(&self) -> String {
+        self.git_username.clone()
+    }
+}
+
+fn main() {
+    let student = CSStudent {
+        name: "Sunfei".to_string(),
+        university: "XXX".to_string(),
+        fav_language: "Rust".to_string(),
+        git_username: "sunface".to_string()
+    };
+
+    println!("{}", comp_sci_student_greeting(&student));
+}
+```
+
+5.
+```rust
+use std::fmt;
+
+// DEFINE a newtype `Pretty`
+struct Pretty(String);
+
+impl fmt::Display for Pretty {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "\"{}\"", self.0.clone() + ", world")
+    }
+}
+
+fn main() {
+    let w = Pretty("hello".to_string());
+    println!("w = {}", w);
+}
+```
\ No newline at end of file
diff --git a/src/SUMMARY.md b/src/SUMMARY.md
index b11aa0e..53b671a 100644
--- a/src/SUMMARY.md
+++ b/src/SUMMARY.md
@@ -27,8 +27,9 @@
   - [Const Generics](generics-traits/const-generics.md)
   - [Traits](generics-traits/traits.md)
   - [Trait Object](generics-traits/trait-object.md)
-  - [Advance Traits](generics-traits/advance-traits.md)
+  - [Advance Traits](generics-traits/advanced-traits.md)
 - [Collection Types todo](collections/intro.md)
+  - [String](collections/string.md)
   - [Vector](collections/vector.md)
   - [HashMap](collections/hashmap.md)
 - [Type Conversion todo](type-conversion.md)
diff --git a/src/collections/string.md b/src/collections/string.md
new file mode 100644
index 0000000..2c0923c
--- /dev/null
+++ b/src/collections/string.md
@@ -0,0 +1 @@
+# String
diff --git a/src/generics-traits/advanced-traits.md b/src/generics-traits/advanced-traits.md
new file mode 100644
index 0000000..c597953
--- /dev/null
+++ b/src/generics-traits/advanced-traits.md
@@ -0,0 +1,277 @@
+# Advance Traits
+
+## Associated types
+The use of "Associated types" improves the overall readability of code by moving inner types locally into a trait as output types. For example :
+```rust
+pub trait CacheableItem: Clone + Default + fmt::Debug + Decodable + Encodable {
+  type Address: AsRef<[u8]> + Clone + fmt::Debug + Eq + Hash;
+  fn is_null(&self) -> bool;
+}
+```
+
+Using of `Address` is much more clearable and convenient than `AsRef<[u8]> + Clone + fmt::Debug + Eq + Hash`.
+
+1. 🌟🌟🌟
+```rust,editable
+
+struct Container(i32, i32);
+
+// USING associated types to re-implement trait Contains.
+// trait Container {
+//    type A;
+//    type B;
+
+trait Contains<A, B> {
+    fn contains(&self, _: &A, _: &B) -> bool;
+    fn first(&self) -> i32;
+    fn last(&self) -> i32;
+}
+
+impl Contains<i32, i32> for Container {
+    fn contains(&self, number_1: &i32, number_2: &i32) -> bool {
+        (&self.0 == number_1) && (&self.1 == number_2)
+    }
+    // Grab the first number.
+    fn first(&self) -> i32 { self.0 }
+
+    // Grab the last number.
+    fn last(&self) -> i32 { self.1 }
+}
+
+fn difference<A, B, C: Contains<A, B>>(container: &C) -> i32 {
+    container.last() - container.first()
+}
+
+fn main() {
+    let number_1 = 3;
+    let number_2 = 10;
+
+    let container = Container(number_1, number_2);
+
+    println!("Does container contain {} and {}: {}",
+        &number_1, &number_2,
+        container.contains(&number_1, &number_2));
+    println!("First number: {}", container.first());
+    println!("Last number: {}", container.last());
+    
+    println!("The difference is: {}", difference(&container));
+}
+```
+
+## Default Generic Type Parameters
+When we use generic type parameters, we can specify a default concrete type for the generic type. This eliminates the need for implementors of the trait to specify a concrete type if the default type works.
+
+2. 🌟🌟
+```rust,editable
+
+use std::ops::Sub;
+
+#[derive(Debug, PartialEq)]
+struct Point<T> {
+    x: T,
+    y: T,
+}
+
+// FILL in the blank in three ways: two of them use the default generic  parameters, the other one not.
+// Notice that the implementation uses the associated type `Output`.
+impl __ {
+    type Output = Self;
+
+    fn sub(self, other: Self) -> Self::Output {
+        Point {
+            x: self.x - other.x,
+            y: self.y - other.y,
+        }
+    }
+}
+
+fn main() {
+    assert_eq!(Point { x: 2, y: 3 } - Point { x: 1, y: 0 },
+        Point { x: 1, y: 3 });
+
+    println!("Success!")
+}
+```
+
+## Fully Qualified Syntax
+othing in Rust prevents a trait from having a method with the same name as another trait’s method, nor does Rust prevent you from implementing both traits on one type. It’s also possible to implement a method directly on the type with the same name as methods from traits.
+
+When calling methods with the same name, we have to use  Fully Qualified Syntax.
+
+#### Example
+```rust,editable
+trait UsernameWidget {
+    // Get the selected username out of this widget
+    fn get(&self) -> String;
+}
+
+trait AgeWidget {
+    // Get the selected age out of this widget
+    fn get(&self) -> u8;
+}
+
+// A form with both a UsernameWidget and an AgeWidget
+struct Form {
+    username: String,
+    age: u8,
+}
+
+impl UsernameWidget for Form {
+    fn get(&self) -> String {
+        self.username.clone()
+    }
+}
+
+impl AgeWidget for Form {
+    fn get(&self) -> u8 {
+        self.age
+    }
+}
+
+fn main() {
+    let form = Form{
+        username: "rustacean".to_owned(),
+        age: 28,
+    };
+
+    // If you uncomment this line, you'll get an error saying 
+    // "multiple `get` found". Because, after all, there are multiple methods
+    // named `get`.
+    // println!("{}", form.get());
+    
+    let username = UsernameWidget::get(&form);
+    assert_eq!("rustacean".to_owned(), username);
+    let age = AgeWidget::get(&form); // you can also use `<Form as AgeWidget>::get`
+    assert_eq!(28, age);
+
+    println!("Success!")
+}
+```
+
+#### Exercise
+3. 🌟🌟
+```rust,editable
+trait Pilot {
+    fn fly(&self) -> String;
+}
+
+trait Wizard {
+    fn fly(&self) -> String;
+}
+
+struct Human;
+
+impl Pilot for Human {
+    fn fly(&self) -> String {
+        String::from("This is your captain speaking.")
+    }
+}
+
+impl Wizard for Human {
+    fn fly(&self) -> String {
+        String::from("Up!")
+    }
+}
+
+impl Human {
+    fn fly(&self) -> String {
+        String::from("*waving arms furiously*")
+    }
+}
+
+fn main() {
+    let person = Human;
+
+    assert_eq!(__, "This is your captain speaking.");
+    assert_eq!(__, "Up!");
+
+    assert_eq!(__, "*waving arms furiously*");
+
+    println!("Success!")
+}
+```
+
+## Supertraits
+Sometimes, you might need one trait to use another trait’s functionality( like the "inheritance" in other languages ). In this case, you need to rely on the dependent trait also being implemented. The trait you rely on is a `supertrait` of the trait you’re implementing.
+
+4. 🌟🌟🌟
+```rust,editable
+
+trait Person {
+    fn name(&self) -> String;
+}
+
+// Person is a supertrait of Student.
+// Implementing Student requires you to also impl Person.
+trait Student: Person {
+    fn university(&self) -> String;
+}
+
+trait Programmer {
+    fn fav_language(&self) -> String;
+}
+
+// CompSciStudent (computer science student) is a subtrait of both Programmer 
+// and Student. Implementing CompSciStudent requires you to impl both supertraits.
+trait CompSciStudent: Programmer + Student {
+    fn git_username(&self) -> String;
+}
+
+fn comp_sci_student_greeting(student: &dyn CompSciStudent) -> String {
+    format!(
+        "My name is {} and I attend {}. My favorite language is {}. My Git username is {}",
+        student.name(),
+        student.university(),
+        student.fav_language(),
+        student.git_username()
+    )
+}
+
+struct CSStudent {
+    name: String,
+    university: String,
+    fav_language: String,
+    git_username: String
+}
+
+// IMPLEMENT the necessary traits for CSStudent to make the code work
+impl ...
+
+fn main() {
+    let student = CSStudent {
+        name: "Sunfei".to_string(),
+        university: "XXX".to_string(),
+        fav_language: "Rust".to_string(),
+        git_username: "sunface".to_string()
+    };
+
+    // FILL in the blank
+    println!("{}", comp_sci_student_greeting(__));
+}
+```
+
+## Orphan Rules
+We can’t implement external traits on external types. For example, we can’t implement the `Display` trait on `Vec<T>` within our own crate, because `Display` and `Vec<T>` are defined in the standard library and aren’t local to our crate. 
+
+This restriction is often called as the orphan rule, so named because the parent type is not present. This rule ensures that other people’s code can’t break your code and vice versa. 
+
+It’s possible to get around this restriction using the newtype pattern, which involves creating a new type in a tuple struct.
+
+5. 🌟🌟
+```rust
+use std::fmt;
+
+// DEFINE a newtype `Pretty` here
+
+
+impl fmt::Display for Pretty {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "\"{}\"", self.0.clone() + ", world")
+    }
+}
+
+fn main() {
+    let w = Pretty("hello".to_string());
+    println!("w = {}", w);
+}
+```
\ No newline at end of file
diff --git a/zh-CN/src/SUMMARY.md b/zh-CN/src/SUMMARY.md
index 52a51d1..7b8e3c7 100644
--- a/zh-CN/src/SUMMARY.md
+++ b/zh-CN/src/SUMMARY.md
@@ -27,7 +27,7 @@
   - [Const 泛型](generics-traits/const-generics.md)
   - [特征 Traits](generics-traits/traits.md)
   - [特征对象](generics-traits/trait-object.md)
-  - [进一步深入特征](generics-traits/advance-traits.md)
+  - [进一步深入特征](generics-traits/advanced-traits.md)
 - [集合类型 todo](collections/intro.md)
   - [动态数组 Vector](collections/vector.md)
   - [KV 存储 HashMap](collections/hashmap.md)
diff --git a/zh-CN/src/generics-traits/advance-traits.md b/zh-CN/src/generics-traits/advance-traits.md
deleted file mode 100644
index 8cd2f63..0000000
--- a/zh-CN/src/generics-traits/advance-traits.md
+++ /dev/null
@@ -1 +0,0 @@
-# Advance Traits
diff --git a/src/generics-traits/advance-traits.md b/zh-CN/src/generics-traits/advanced-traits.md
similarity index 100%
rename from src/generics-traits/advance-traits.md
rename to zh-CN/src/generics-traits/advanced-traits.md