策略模式在Thread和Runnable中的應用分析 這里以實現個人所得稅的計算功能為例，一步步來模擬Runnable的樣子來優化代碼： 模板方法 ```java /** * @program: ThreadDemo * @description: 計算稅率：工資*0.1 + 獎金*0.15 * @author: hs96.cn@Gmail.com * @create: 2020-08-28 */ public class TaxCalculatorMain { public static void main(String[] args) { TaxCalculator taxCalculator = new TaxCalculator(10000d, 2000d) { @Override protected double calcTax() { return getSalary() * 0.1 + getBonus() * 0.15; } }; double tax = taxCalculator.calculate(); System.out.println(tax); } } ``` ```java /** * @program: ThreadDemo * @description: 個人所得稅計算器 * @author: hs96.cn@Gmail.com * @create: 2020-08-28 */ public class TaxCalculator { // 薪水 private final double salary; // 獎金 private final double bonus; public TaxCalculator(double salary, double bonus) { this.salary = salary; this.bonus = bonus; } public double getSalary() { return salary; } public double getBonus() { return bonus; } protected double calcTax() { return 0.00; } public double calculate() { return calcTax(); } } ``` calculate可以理解為Thread的start方法，他return calcTax();可以理解為start()調用Runnable的run方法。 這樣實現個人所得稅計算器是沒問題的，但是如果在真實的商業應用中就得去改對應界面的代碼，這從設計開閉原則來說就不符合了，所以這里抽象一個計算稅率的接口出來專門來做這個計算，改造代碼如下： 首先我們抽象一個計算稅率的接口出來專門來做計算： ```java @FunctionalInterface public interface CalculatorStrategy { /** * * @param salary 薪水 * @param bonus 獎金 * @return 稅收 */ double calculate(double salary, double bonus); } ``` 接下來我們把具體實現流程放在實現類中： ```java /** * @program: ThreadDemo * @description: 計算稅率：工資*0.1 + 獎金*0.15 * @author: hs96.cn@Gmail.com * @create: 2020-08-28 */ public class SimpleCalculatorStrategy implements CalculatorStrategy { private final static double SALARY_RATE = 0.1; private final static double BONUS_RATE = 0.15; @Override public double calculate(double salary, double bonus) { return salary * SALARY_RATE + bonus * BONUS_RATE; } } ``` 修改main方法如下： ```java /** * @program: ThreadDemo * @description: 計算稅率：工資*0.1 + 獎金*0.15 * @author: hs96.cn@Gmail.com * @create: 2020-08-28 */ public class TaxCalculatorMain { public static void main(String[] args) { //使用摸板方法 /*TaxCalculator taxCalculator = new TaxCalculator(10000d, 2000d) { @Override protected double calcTax() { return getSalary() * 0.1 + getBonus() * 0.15; } }; double tax = taxCalculator.calculate(); System.out.println(tax);*/ //使用策略模式 CalculatorStrategy strategy = new SimpleCalculatorStrategy(); TaxCalculator calculator = new TaxCalculator(10000d, 2000d,strategy); double tex = calculator.calculate(); System.out.println(tex); } } ``` 計算調用算法的類如下： ```java /** * @program: ThreadDemo * @description: 個人所得稅計算器 * @author: hs96.cn@Gmail.com * @create: 2020-08-28 */ public class TaxCalculator { // 薪水 private final double salary; // 獎金 private final double bonus; //計算策略類 private CalculatorStrategy calculatorStrategy; public TaxCalculator(double salary, double bonus, CalculatorStrategy calculatorStrategy) { this.salary = salary; this.bonus = bonus; this.calculatorStrategy = calculatorStrategy; } public double getSalary() { return salary; } public double getBonus() { return bonus; } protected double calcTax() { return calculatorStrategy.calculate(salary, bonus); } public double calculate() { return calcTax(); } } ``` 這里其實主要增加了 CalculatorStrategy對象和calcTax的實現調用了實現算法接口的實現類。 main方法的CalculatorStrategy 就相當于Thread的Runnable 接下來我們加入java8的Lambda表達式來精簡一下代碼： ```java public class TaxCalculatorMain { public static void main(String[] args) { //使用java8的Lambda表達式 TaxCalculator calculator = new TaxCalculator(10000d, 2000d, (s, b) -> s * 0.1 + b * 0.15); System.out.println(calculator.calculate()); } } ``` 可以看到代碼精簡很多。