Java Community | Help. Code. Learn.•13mo ago•

23 replies

how does open-closed principle really work?

hey guys. i have a question an id like to hear other opinions. lets say i have this.:

public class MyService{
  //class fields, getters, setters
  public myServiceMethod(Car car){
    if(car.getColor()=="Red"){
      Print("Red car");
    }
    if(car.getColor()=="Green"){
        Print("Green car");
      }
    //do other business logic
  }
}

public class MyService{
  //class fields, getters, setters
  public myServiceMethod(Car car){
    if(car.getColor()=="Red"){
      Print("Red car");
    }
    if(car.getColor()=="Green"){
        Print("Green car");
      }
    //do other business logic
  }
}

it works fine. but then there comes a point when i need to check if the car is

Yellow

Yellow

and

Blue

Blue

. then it means i have to add more if statements:

public class MyService{
  //class fields, getters, setters
  public myServiceMethod(Car car){
    if(car.getColor()=="Red"){
      Print("Red car");
    }
    if(car.getColor()=="Green"){
        Print("Green car");
    }
    if(car.getColor()=="Yellow"){
        Print("Yellow car");
    }
    if(car.getColor()=="Blue"){
        Print("Blue car");
    }
    //do other business logic
  }
}

public class MyService{
  //class fields, getters, setters
  public myServiceMethod(Car car){
    if(car.getColor()=="Red"){
      Print("Red car");
    }
    if(car.getColor()=="Green"){
        Print("Green car");
    }
    if(car.getColor()=="Yellow"){
        Print("Yellow car");
    }
    if(car.getColor()=="Blue"){
        Print("Blue car");
    }
    //do other business logic
  }
}

now the questions arise:
1. is adding more if statements considered to be

extension

extension

modification

modification

? In my understanding its both. You modify code all the time. You changed variable name? Its modification. In Cambridge dictionary

modification

modification

is described as

a change to something

a change to something

. Refactoring is modification too. You cant write excellent code from the first try.
2. does the first and second pieces of code follow

open-closed

open-closed

principle? why?

JC|HCL

Java Community | Help. Code. Learn.•13mo ago•

23 replies

bambizas19

how does open-closed principle really work?

hey guys. i have a question an id like to hear other opinions. lets say i have this.:

public class MyService{
  //class fields, getters, setters
  public myServiceMethod(Car car){
    if(car.getColor()=="Red"){
      Print("Red car");
    }
    if(car.getColor()=="Green"){
        Print("Green car");
      }
    //do other business logic
  }
}

public class MyService{
  //class fields, getters, setters
  public myServiceMethod(Car car){
    if(car.getColor()=="Red"){
      Print("Red car");
    }
    if(car.getColor()=="Green"){
        Print("Green car");
      }
    //do other business logic
  }
}

it works fine. but then there comes a point when i need to check if the car is

Yellow

Yellow

and

Blue

Blue

. then it means i have to add more if statements:

public class MyService{
  //class fields, getters, setters
  public myServiceMethod(Car car){
    if(car.getColor()=="Red"){
      Print("Red car");
    }
    if(car.getColor()=="Green"){
        Print("Green car");
    }
    if(car.getColor()=="Yellow"){
        Print("Yellow car");
    }
    if(car.getColor()=="Blue"){
        Print("Blue car");
    }
    //do other business logic
  }
}

public class MyService{
  //class fields, getters, setters
  public myServiceMethod(Car car){
    if(car.getColor()=="Red"){
      Print("Red car");
    }
    if(car.getColor()=="Green"){
        Print("Green car");
    }
    if(car.getColor()=="Yellow"){
        Print("Yellow car");
    }
    if(car.getColor()=="Blue"){
        Print("Blue car");
    }
    //do other business logic
  }
}

now the questions arise:
1. is adding more if statements considered to be

extension

extension

modification

modification

? In my understanding its both. You modify code all the time. You changed variable name? Its modification. In Cambridge dictionary

modification

modification

is described as

a change to something

a change to something

. Refactoring is modification too. You cant write excellent code from the first try.
2. does the first and second pieces of code follow

open-closed

open-closed

principle? why?

how does open-closed principle really work?

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