重構-Extract Method

Before

package com.lohamce.refactor;

import java.util.List;

public class ExtractMethod {
	
	
	private String name;
	private List<Order> orders;

	void printOwing(double previousAmount) {
		
		List<Order> myOrder = orders;
		
		double outstanding = previousAmount * 1.2;
		
		
		// Print Banner
		System.out.println("**************************");
		System.out.println("****Customer Owes*********");
		System.out.println("**************************");
		

		for (Order order : myOrder) {
			outstanding += order.getAmount();
		}
		
		// print details
		System.out.print("name:"+name);
		System.out.print("amount:"+outstanding);
	}


}


class Order {
	
	private double amount;

	public double getAmount() {
		return amount;
	}

	public void setAmount(double amount) {
		this.amount = amount;
	}
	
}           

After

package com.lohamce.refactor;

import java.util.List;

public class ExtractMethod2 {
	
	
	private String name;
	private List<Order> orders;

	void printOwing(double previousAmount) {
		
		printBanner();
		
		// 因為outstanding被改變了, 是以需要定義一個變量以後使用
		double outstanding = getOutstanding(previousAmount * 1.2);

		printDetails(outstanding);
	}
	

	
	// 不改變原始值, 傳回一個結果值
	private double getOutstanding(double initialValue) {
		double result = initialValue;
		for (Order order : orders) {
			result += order.getAmount();
		}
		
		return result;
	}



	private void printDetails(double outstanding) {

		System.out.print("name:"+name);
		System.out.print("amount:"+outstanding);
		
	}



	private void printBanner(){
		
		System.out.println("**************************");
		System.out.println("****Customer Owes*********");
		System.out.println("**************************");
	}


}