建構函式引用

建構函式引用有助於指向建構函式方法。建構函式引用透過“::new”符號進行訪問。

//Constructor reference
Factory vehicle_factory = Vehicle::new;       

以下示例展示了 Java 8 及更高版本中建構函式引用的工作方式。

interface Factory {
   Vehicle prepare(String make, String model, int year);
}

class Vehicle {
   private String make;
   private String model;
   private int year;

   Vehicle(String make, String model, int year){
      this.make = make;
      this.model = model;
      this.year = year;
   }

   public String toString(){
      return "Vehicle[" + make +", " + model + ", " + year+ "]";
   }    
}

public class FunctionTester {
   static Vehicle factory(Factory factoryObj, String make, String model, int year){
      return factoryObj.prepare(make, model, year);
   }

   public static void main(String[] args) {       
      //Constructor reference
      Factory vehicle_factory = Vehicle::new;
      Vehicle carHonda = factory(vehicle_factory, "Honda", "Civic", 2017);
      System.out.println(carHonda);
   } 
}

輸出

Vehicle[Honda, Civic, 2017]