JAVA应用之if-else 的优化

bug的搬运工 08-04 143

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使用多态或策略模式：将条件判断转换为对象的行为，减少 if-else 的使用。

public interface DiscountStrategy {    double applyDiscount(double amount);}public class SeniorDiscountStrategy implements DiscountStrategy {    @Override    public double applyDiscount(double amount) {        // 计算老年人优惠后的价格        return amount * 0.9;    }}public class StudentDiscountStrategy implements DiscountStrategy {    @Override    public double applyDiscount(double amount) {        // 计算学生优惠后的价格        return amount * 0.8;    }}public class DiscountCalculator {    private DiscountStrategy discountStrategy;    public void setDiscountStrategy(DiscountStrategy discountStrategy) {        this.discountStrategy = discountStrategy;    }    public double calculateDiscount(double amount) {        return discountStrategy.applyDiscount(amount);    }}// 使用示例DiscountCalculator calculator = new DiscountCalculator();calculator.setDiscountStrategy(new SeniorDiscountStrategy());double discountedPrice = calculator.calculateDiscount(100.0);

使用工厂模式：通过工厂类创建对象，避免直接使用 if-else 进行对象的创建。

public interface DiscountStrategy {    double applyDiscount(double amount);}public class SeniorDiscountStrategy implements DiscountStrategy {    @Override    public double applyDiscount(double amount) {        // 计算老年人优惠后的价格        return amount * 0.9;    }}public class StudentDiscountStrategy implements DiscountStrategy {    @Override    public double applyDiscount(double amount) {        // 计算学生优惠后的价格        return amount * 0.8;    }}public class DiscountStrategyFactory {    public static DiscountStrategy createDiscountStrategy(String userType) {        if (userType.equalsIgnoreCase("senior")) {            return new SeniorDiscountStrategy();        } else if (userType.equalsIgnoreCase("student")) {            return new StudentDiscountStrategy();        }        return null;    }}// 使用示例DiscountStrategy discountStrategy = DiscountStrategyFactory.createDiscountStrategy("senior");double discountedPrice = discountStrategy.applyDiscount(100.0);

使用 Map 或策略映射：将条件与对应的操作存储在 Map 中，根据条件查找对应的操作进行执行。

public class DiscountCalculator {    private Map<String, DiscountStrategy> discountStrategies;    public DiscountCalculator() {        discountStrategies = new HashMap<>();        discountStrategies.put("senior", new SeniorDiscountStrategy());        discountStrategies.put("student", new StudentDiscountStrategy());    }    public double calculateDiscount(String userType, double amount) {        DiscountStrategy discountStrategy = discountStrategies.get(userType);        if (discountStrategy != null) {            return discountStrategy.applyDiscount(amount);        }        return amount;    }}// 使用示例DiscountCalculator calculator = new DiscountCalculator();double discountedPrice = calculator.calculateDiscount("senior", 100.0);

4、使用枚举优化

public enum DiscountType {    SENIOR {        @Override        public double applyDiscount(double amount) {            // 计算老年人优惠后的价格            return amount * 0.9;        }    },    STUDENT {        @Override        public double applyDiscount(double amount) {            // 计算学生优惠后的价格            return amount * 0.8;        }    };    public abstract double applyDiscount(double amount);}// 使用示例DiscountType discountType = DiscountType.SENIOR;double discountedPrice = discountType.applyDiscount(100.0);

通过枚举类型，可以将不同条件的操作逻辑封装在枚举常量中，使用起来更加简洁和易于扩展。

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