Java 8 method references and construction reference code instances

This article mainly introduces java8 method reference and construction reference code examples. The example code is introduced in great detail, which has certain reference value for everyone's study or work. Friends in need can refer to it

I. overview of method reference

Method reference is a shorthand for a specific lamda expression. Its idea is to directly call the function and use the method name if it can replace the lamda expression. Its syntax format: Class Name:: method name.

II. Three methods of reference

1 reference to static method

Syntax format: static class name: method name

Example:

  // 1 Lamda静态方法
  @Test
  public void LamdaStest(){
    String youku1327 = "1327";
    Function function = s -> ObjectUtils.allNotNull(youku1327);
    System.out.println(function.apply(youku1327));// true

  }
  // 静态方法引用
  @Test
  public void MethodReftest(){
    String youku1327 = "youku1327";
    Function function = ObjectUtils::allNotNull;
    System.out.println(function.apply(youku1327));// true
  }

2 reference to the method of the object instance

Syntax format: instance name: method name

This object refers to an external object that is not an input parameter

Example:

  // 2 Lamda表达式
  @Test
  public void ObjectLamdatest(){
    Car car = new Car("100","black","中国",20);
    supplier supplier = ()-> car.getColor();
    System.out.println(supplier.get());//black
  }
  // 对象引用
  @Test
  public void ObjectReftest(){
    Car car = new Car("100",20);
    supplier<String> supplier = car::getColor;
    System.out.println(supplier.get());//black
  }

3 method reference to instance

Syntax format: object name (classname):: method name. This object refers to the input parameter object

  //3 Lamda表达式
  @Test
  public void InstanceMethodLamdatest(){
    Car car = new Car("100",20);
    Function<Car,String> function = s -> s.getColor();
    System.out.println(function.apply(car));//black
  }

  @Test
  public void InstanceMethodReftest(){
    Car car = new Car("100",String> function = Car::getColor;
    System.out.println(function.apply(car));//black
  }

Three constructor references

Syntax format: object name (classname):: New

  @Test
  public void constructLamdatest(){
    BiFunction<String,Double,Car> biFunction = (s,aDouble) -> new Car(s,aDouble);
    Car car = biFunction.apply("youku1327",50.0);
    // Car(code=youku1327,color=null,factory=null,price=50.0)
    System.out.println(car);
  }

  @Test
  public void construcMethodReftest(){
    BiFunction<String,Car> biFunction = Car::new;
    Car car = biFunction.apply("youku1327",price=50.0)
    System.out.println(car);
  }

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