Replace Parameter with Explicit Methods

 

before

public class ReplaceParameterWithExplicitMethod_before {

	static final int ENGINEER = 0;
	static final int SALESMAN = 1;
	static final int MANAGER = 2;

	static public class Employee {
		// ...		
		private int type;
		
		private Employee(int type) {
			this.type = type;
		}
		
		static Employee create(int type) {
			switch (type) {
				case ENGINEER:
					return new Engineer();
				case SALESMAN:
					return new Salesman();
				case MANAGER:
					return new Manager();
				default:
					throw new IllegalArgumentException("Incorrect type code value");
			}
		}
		
		public String getName() {
			String name = "None";
			switch(type) {
			case ENGINEER:
				name = "ENGINEER"; break;
			case SALESMAN:
				name = "SALESMAN"; break;
			case MANAGER:
				name = "MANAGER"; break;
			}
			return name;
		}
	}
	
	static class Engineer extends Employee {
		public Engineer() {
			super(ENGINEER);
		}
	}
	static class Salesman extends Employee {
		public Salesman() {
			super(SALESMAN);
		}
	}
	static class Manager extends Employee {
		public Manager() {
			super(MANAGER);
		}
	}
	
	public static void main(String[] args) {
		Employee kent = Employee.create(ENGINEER);
		System.out.println(kent.getName());
	}

}

 

after

public class ReplaceParameterWithExplicitMethod_before {

	static final int ENGINEER = 0;
	static final int SALESMAN = 1;
	static final int MANAGER = 2;

	static public class Employee {
		// ...		
		private int type;
		
		private Employee(int type) {
			this.type = type;
		}
		
		static Employee create(int type) {
			switch (type) {
				case ENGINEER:
					return createEngineer();
				case SALESMAN:
					return createSalesman();
				case MANAGER:
					return createManager();
				default:
					throw new IllegalArgumentException("Incorrect type code value");
			}
		}

		public static Engineer createEngineer() {
			return new Engineer();
		}

		public static Salesman createSalesman() {
			return new Salesman();
		}

		public static Manager createManager() {
			return new Manager();
		}

		public String getName() {
			String name = "None";
			switch(type) {
			case ENGINEER:
				name = "ENGINEER"; break;
			case SALESMAN:
				name = "SALESMAN"; break;
			case MANAGER:
				name = "MANAGER"; break;
			}
			return name;
		}
	}
	
	static class Engineer extends Employee {
		public Engineer() {
			super(ENGINEER);
		}
	}
	static class Salesman extends Employee {
		public Salesman() {
			super(SALESMAN);
		}
	}
	static class Manager extends Employee {
		public Manager() {
			super(MANAGER);
		}
	}
	
	public static void main(String[] args) {
		Employee kent = Employee.createEngineer(); //이거 이렇게 할 수 있다
		System.out.println(kent.getName());
	}

}