小白写了一堆if-else，大神实在看不下去了，竟然用策略模式直接摆平了

/**
 * 策略模式演示类
 */
public class MyService {

    /**
     * 使用if-else的解决方案
     */
    public String processResult(String key) {
        if ("checkvalue1".equals(key)) {
            return "business logic1";   
        } else if ("checkvalue2".equals(key)) {
            return "business logic2";
        }else if ("checkvalue3".equals(key)) {
            return "business logic3";
        }else if ("checkvalue4".equals(key)) {
            return "business logic4";
        }else if ("checkvalue5".equals(key)) {
            return "business logic5";
        }else if ("checkvalue6".equals(key)) {
            return "business logic6";
        }else if ("checkvalue7".equals(key)) {
            return "business logic7";
        }else if ("checkvalue8".equals(key)) {
            return "business logic8";
        }else if ("checkvalue9".equals(key)) {
            return "business logic9";
        }
        return "error;
    }

    /**
     * 用于业务逻辑分派Map
     * Function为函数式接口，下面代码中 Function<String, String> 的含义是接收一个String类型的变量，返回一个String类型的结果
     */
    private Map<String, Function<String, String>> myDispatcher = new HashMap<>();

    /**
     * 使用策略模式的方法
     */
  
    public void  policyInit() {
        myDispatcher.put("checkvalue1", key -> String.format("business logic1 for %s1", key));
        myDispatcher.put("checkvalue2", key -> String.format("business logic2 for %s2", key));
        myDispatcher.put("checkvalue3", key -> String.format("business logic3 for %s3", key));
        myDispatcher.put("checkvalue4", key -> String.format("business logic4 for %s4", key));
        myDispatcher.put("checkvalue5", key -> String.format("business logic5 for %s5", key));
        myDispatcher.put("checkvalue6", key -> String.format("business logic6 for %s6", key));
        myDispatcher.put("checkvalue7", key -> String.format("business logic7 for %s7", key));
        myDispatcher.put("checkvalue8", key -> String.format("business logic8 for %s8", key));
        myDispatcher.put("checkvalue9", key -> String.format("business logic9 for %s9", key));
    }

    public String processPolicyResult(String key) {
        //从逻辑分派Dispatcher中获得业务逻辑代码，result变量是一个lambda表达式
        Function<String, String> result = myDispatcher.get(key);
        if (result != null) {
            //执行这段表达式获得String类型的结果
            return result.apply(key);
        }
        return "error";
    }
}

下面是调用代码：

public class RunPolicy {
    private MyService myService;

    public String test(String key) {
        return myService.processPolicyResult(order);
    }
}

从这段代码中可以看到很多好处，例如：

/**
 * 专门放业务逻辑的服务类
 */
public class ServiceUnit {

    public String task1(String key) {
        return "业务逻辑1";
    }
    public String task2(String key) {
        return "业务逻辑2";
    }
     public String task3(String key) {
        return "业务逻辑3";
    }
     public String task4(String key) {
        return "业务逻辑4";
    }
}
/**
 * 使用策略模式的类
 */
public class PolicyService {
    private ServiceUnit serviceUnit;

    private Map<String, Function<String, String>> myDispatcher = new HashMap<>();

    /**
     * 初始化规则映射
     */
    public void dispatcherInit() {
        myDispatcher.put("key_order1", key -> serviceUnit.task1(key));
        myDispatcher.put("key_order1_order2", key -> serviceUnit.task2(key)));
        myDispatcher.put("key_order1_order2_order3", key -> serviceUnit.task3(key));
        myDispatcher.put("key_order1_order2_order3_order4", key -> serviceUnit.task4(key));
    }

    public String process(String key, int level) {
        // 根据level生成对应的key
        String dKey = getDispatcherKey(key, level);

        Function<String, String> result = myDispatcher.get(dKey);
        if (result != null) {
            //执行这段表达式获得String类型的结果
            return result.apply(order);
        }
        return "error";
    }

    /**
     * 根据level生成对应的key
     */
    private String getDispatcherKey(String key, int level) {
        StringBuilder k = new StringBuilder("key");
        for (int i = 1; i <= level; i++) {
            k.append("_" + order + i);
        }
        return k.toString();
    }
}

总结：