模板方法模式

小鱼儿 2022-06-03 02:41 54阅读 0赞

**模板方法模式**：在一个方法中定义一个算法的骨架，而将一些步骤延迟到子类中。模板方法使得子类可以在不改变算法的结构的情况下，重新定义算法中的某些步骤。

模板方法模式类图：

![输入图片说明][14084130_co0X.png]

模板方法模式的用意：准备一个抽象类，将部分逻辑以具体方法以及具体构造子的形式实现，然后声明一些抽象方法来迫使子类实现剩余的逻辑。不同的子类可以以不同的方式实现这些抽象方法，从而对剩余的逻辑有不同的实现。代码如下：

package templateMethod;
    public abstract class CaffeineBeverageWithHook {
    
        void prepareRecipe() {
            boilWater();
            brew();
            pourInCup();
            if (customerWantsCondiments()) {
                addCondiments();
            }
        }
    
        abstract void brew();
    
        abstract void addCondiments();
    
        void boilWater() {
            System.out.println("Boiling water");
        }
    
        void pourInCup() {
            System.out.println("Pouring into cup");
        }
    
        boolean customerWantsCondiments() {
            return true;
        }
    }

package templateMethod;
    import java.io.*;
    public class TeaWithHook extends CaffeineBeverageWithHook { 
    
        public void brew() {
            System.out.println("Steeping the tea");
        }
    
        public void addCondiments() {
            System.out.println("Adding Lemon");
        }
    
        public boolean customerWantsCondiments() {
    
            String answer = getUserInput();
    
            if (answer.toLowerCase().startsWith("y")) {
                return true;
            } else {
                return false;
            }
        }
    
        private String getUserInput() {
            // get the user's response
            String answer = null;
    
            System.out.print("Would you like milk and sugar with your coffee (y/n)? ");
    
            BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
            try {
                answer = in.readLine();
            } catch (IOException ioe) {
                System.err.println("IO error trying to read your answer");
            }
            if (answer == null) {
                return "no";
            }
            return answer;
        }
    }

package templateMethod;
    import java.io.*;
    public class CoffeeWithHook extends CaffeineBeverageWithHook { 
    
        public void brew() {
            System.out.println("Dripping Coffee through filter");
        }
    
        public void addCondiments() {
            System.out.println("Adding Sugar and Milk");
        }
    
        public boolean customerWantsCondiments() {
    
            String answer = getUserInput();
    
            if (answer.toLowerCase().startsWith("y")) {
                return true;
            } else {
                return false;
            }
        }
    
        private String getUserInput() {
            String answer = null;
    
            System.out.print("Would you like milk and sugar with your coffee (y/n)? ");
    
            BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
            try {
                answer = in.readLine();
            } catch (IOException ioe) {
                System.err.println("IO error trying to read your answer");
            }
            if (answer == null) {
                return "no";
            }
            return answer;
        }
    }

package templateMethod;
    public class BeverageTestDrive {
        public static void main(String[] args) {
    
            TeaWithHook teaHook = new TeaWithHook();
            CoffeeWithHook coffeeHook = new CoffeeWithHook();
    
            System.out.println("\nMaking tea...");
            teaHook.prepareRecipe();
    
            System.out.println("\nMaking coffee...");
            coffeeHook.prepareRecipe();
        }
    }

[14084130_co0X.png]: https://static.oschina.net/uploads/img/201712/14084130_co0X.png