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本文小編為大家詳細(xì)介紹“java中如何優(yōu)化大量if...else...”,內(nèi)容詳細(xì),步驟清晰,細(xì)節(jié)處理妥當(dāng),希望這篇“java中如何優(yōu)化大量if...else...”文章能幫助大家解決疑惑,下面跟著小編的思路慢慢深入,一起來(lái)學(xué)習(xí)新知識(shí)吧。
將每個(gè)條件分支的實(shí)現(xiàn)作為一個(gè)獨(dú)立的策略類,然后使用一個(gè)上下文對(duì)象來(lái)選擇要執(zhí)行的策略。這種方法可以將大量的if else語(yǔ)句轉(zhuǎn)換為對(duì)象之間的交互,從而提高代碼的可維護(hù)性和可擴(kuò)展性。
示例:
首先,我們定義一個(gè)接口來(lái)實(shí)現(xiàn)所有策略的行為:
public interface PaymentStrategy { void pay(double amount); }
接下來(lái),我們定義具體的策略類來(lái)實(shí)現(xiàn)不同的支付方式:
public class CreditCardPaymentStrategy implements PaymentStrategy { private String name; private String cardNumber; private String cvv; private String dateOfExpiry; public CreditCardPaymentStrategy(String name, String cardNumber, String cvv, String dateOfExpiry) { this.name = name; this.cardNumber = cardNumber; this.cvv = cvv; this.dateOfExpiry = dateOfExpiry; } public void pay(double amount) { System.out.println(amount + " paid with credit card"); } } public class PayPalPaymentStrategy implements PaymentStrategy { private String emailId; private String password; public PayPalPaymentStrategy(String emailId, String password) { this.emailId = emailId; this.password = password; } public void pay(double amount) { System.out.println(amount + " paid using PayPal"); } } public class CashPaymentStrategy implements PaymentStrategy { public void pay(double amount) { System.out.println(amount + " paid in cash"); } }
現(xiàn)在,我們可以在客戶端代碼中創(chuàng)建不同的策略對(duì)象,并將它們傳遞給一個(gè)統(tǒng)一的支付類中,這個(gè)支付類會(huì)根據(jù)傳入的策略對(duì)象來(lái)調(diào)用相應(yīng)的支付方法:
public class ShoppingCart { private List<Item> items; public ShoppingCart() { this.items = new ArrayList<>(); } public void addItem(Item item) { this.items.add(item); } public void removeItem(Item item) { this.items.remove(item); } public double calculateTotal() { double sum = 0; for (Item item : items) { sum += item.getPrice(); } return sum; } public void pay(PaymentStrategy paymentStrategy) { double amount = calculateTotal(); paymentStrategy.pay(amount); } }
現(xiàn)在我們可以使用上述代碼來(lái)創(chuàng)建一個(gè)購(gòu)物車,向其中添加一些商品,然后使用不同的策略來(lái)支付:
public class Main { public static void main(String[] args) { ShoppingCart cart = new ShoppingCart(); Item item1 = new Item("1234", 10); Item item2 = new Item("5678", 40); cart.addItem(item1); cart.addItem(item2); // pay by credit card cart.pay(new CreditCardPaymentStrategy("John Doe", "1234567890123456", "786", "12/22")); // pay by PayPal cart.pay(new PayPalPaymentStrategy("myemail@example.com", "mypassword")); // pay in cash cart.pay(new CashPaymentStrategy()); //--------------------------或者提前將不同的策略對(duì)象放入map當(dāng)中,如下 Map<String, PaymentStrategy> paymentStrategies = new HashMap<>(); paymentStrategies.put("creditcard", new CreditCardPaymentStrategy("John Doe", "1234567890123456", "786", "12/22")); paymentStrategies.put("paypal", new PayPalPaymentStrategy("myemail@example.com", "mypassword")); paymentStrategies.put("cash", new CashPaymentStrategy()); String paymentMethod = "creditcard"; // 用戶選擇的支付方式 PaymentStrategy paymentStrategy = paymentStrategies.get(paymentMethod); cart.pay(paymentStrategy); } }
將每個(gè)條件分支的實(shí)現(xiàn)作為一個(gè)獨(dú)立的產(chǎn)品類,然后使用一個(gè)工廠類來(lái)創(chuàng)建具體的產(chǎn)品對(duì)象。這種方法可以將大量的if else語(yǔ)句轉(zhuǎn)換為對(duì)象的創(chuàng)建過(guò)程,從而提高代碼的可讀性和可維護(hù)性。
示例:
// 定義一個(gè)接口 public interface StringProcessor { public void processString(String str); } // 實(shí)現(xiàn)接口的具體類 public class LowercaseStringProcessor implements StringProcessor { public void processString(String str) { System.out.println(str.toLowerCase()); } } public class UppercaseStringProcessor implements StringProcessor { public void processString(String str) { System.out.println(str.toUpperCase()); } } public class ReverseStringProcessor implements StringProcessor { public void processString(String str) { StringBuilder sb = new StringBuilder(str); System.out.println(sb.reverse().toString()); } } // 工廠類 public class StringProcessorFactory { public static StringProcessor createStringProcessor(String type) { if (type.equals("lowercase")) { return new LowercaseStringProcessor(); } else if (type.equals("uppercase")) { return new UppercaseStringProcessor(); } else if (type.equals("reverse")) { return new ReverseStringProcessor(); } throw new IllegalArgumentException("Invalid type: " + type); } } // 測(cè)試代碼 public class Main { public static void main(String[] args) { StringProcessor sp1 = StringProcessorFactory.createStringProcessor("lowercase"); sp1.processString("Hello World"); StringProcessor sp2 = StringProcessorFactory.createStringProcessor("uppercase"); sp2.processString("Hello World"); StringProcessor sp3 = StringProcessorFactory.createStringProcessor("reverse"); sp3.processString("Hello World"); } }
看起來(lái)還是有if...else,但這樣的代碼更加簡(jiǎn)潔易懂,后期也便于維護(hù)....
使用一個(gè)映射表來(lái)將條件分支的實(shí)現(xiàn)映射到對(duì)應(yīng)的函數(shù)或方法上。這種方法可以減少代碼中的if else語(yǔ)句,并且可以動(dòng)態(tài)地更新映射表,從而提高代碼的靈活性和可維護(hù)性。
示例:
import java.util.HashMap; import java.util.Map; import java.util.function.Function; public class MappingTableExample { private Map<String, Function<Integer, Integer>> functionMap; public MappingTableExample() { functionMap = new HashMap<>(); functionMap.put("add", x -> x + 1); functionMap.put("sub", x -> x - 1); functionMap.put("mul", x -> x * 2); functionMap.put("div", x -> x / 2); } public int calculate(String operation, int input) { if (functionMap.containsKey(operation)) { return functionMap.get(operation).apply(input); } else { throw new IllegalArgumentException("Invalid operation: " + operation); } } public static void main(String[] args) { MappingTableExample example = new MappingTableExample(); System.out.println(example.calculate("add", 10)); System.out.println(example.calculate("sub", 10)); System.out.println(example.calculate("mul", 10)); System.out.println(example.calculate("div", 10)); System.out.println(example.calculate("mod", 10)); // 拋出異常 } }
將條件分支的實(shí)現(xiàn)和輸入數(shù)據(jù)一起存儲(chǔ)在一個(gè)數(shù)據(jù)結(jié)構(gòu)中,然后使用一個(gè)通用的函數(shù)或方法來(lái)處理這個(gè)數(shù)據(jù)結(jié)構(gòu)。這種方法可以將大量的if else語(yǔ)句轉(zhuǎn)換為數(shù)據(jù)結(jié)構(gòu)的處理過(guò)程,從而提高代碼的可擴(kuò)展性和可維護(hù)性。
示例:
import java.util.ArrayList; import java.util.List; import java.util.function.Function; public class DataDrivenDesignExample { private List<Function<Integer, Integer>> functionList; public DataDrivenDesignExample() { functionList = new ArrayList<>(); functionList.add(x -> x + 1); functionList.add(x -> x - 1); functionList.add(x -> x * 2); functionList.add(x -> x / 2); } public int calculate(int operationIndex, int input) { if (operationIndex < 0 || operationIndex >= functionList.size()) { throw new IllegalArgumentException("Invalid operation index: " + operationIndex); } return functionList.get(operationIndex).apply(input); } public static void main(String[] args) { DataDrivenDesignExample example = new DataDrivenDesignExample(); System.out.println(example.calculate(0, 10)); System.out.println(example.calculate(1, 10)); System.out.println(example.calculate(2, 10)); System.out.println(example.calculate(3, 10)); System.out.println(example.calculate(4, 10)); // 拋出異常 } }
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