java 使用策略模式解決代碼中包含太多的if else

1.首先創建一個enum枚舉類

　　　　代碼附上：

public enum SystemErrorCode {
    QUIT(":quit", "", "com.pluster.cloudshiro.utils.PrintQuitCommand"),
    ALL(":all", "", "com.pluster.cloudshiro.utils.PrintAllCommand"),
    USER(":user", "", "com.pluster.cloudshiro.utils.PrintUserCommand"),
    ADMIN(":admin", "", "com.pluster.cloudshiro.utils.PrintAdminCommand"),
    AI(":ai", "", "com.pluster.cloudshiro.utils.PrintAiCommand"),
    QAI(":qai", "", "com.pluster.cloudshiro.utils.PrintQaiCommand"),
    INFO(":info", "", "com.pluster.cloudshiro.utils.PrintInfoCommand");
    private String code;
    private String desc;
    private String clazz;
    private static final Map<String, String> err_desc = new HashMap<String, String>();

    static {
        for (SystemErrorCode refer : SystemErrorCode.values()) {
            err_desc.put(refer.getCode(), refer.getClazz());
        }
    }

    private SystemErrorCode(String code, String desc, String clazz) {
        this.code = code;
        this.desc = desc;
        this.clazz = clazz;
    }

    public static Map<String, String> getAllClazz() {
        return err_desc;
    }
    public static String getDescByCode(int code) {
        return err_desc.get(code);
    }
    public String getCode() {
        return code;
    }
    public void setCode(String code) {
        this.code = code;
    }
    public String getDesc() {
        return desc;
    }
    public void setDesc(String desc) {
        this.desc = desc;
    }
    public String getClazz() {
        return clazz;
    }
    public void setClazz(String clazz) {
        this.clazz = clazz;
    }
}

2.定義策略上下文，根據command獲取對象實例
代碼如下：

public class InnerCommandContext {
    @Autowired
    static ApplicationContext applicationContext;

    public static InnerCommand getInstance(String command) {
        //getAllClazz
        Map<String, String> allClazz = SystemErrorCode.getAllClazz();
        String[] trim = command.trim().split(" ");
        String clazz = allClazz.get(trim[0]);
        InnerCommand innerCommand = null;
        try {
            if (StringUtils.isEmpty(clazz)) {
                clazz = null;
            }
            innerCommand = (InnerCommand) Class.forName(clazz).newInstance();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return innerCommand;
    }
}

3.定義接口
代碼如下：

public interface InnerCommand {
    void process(String msg);
}

4.定義實現類（這里只加了一個實現類，可根據自己業務實現）
代碼如下：

public class PrintAdminCommand implements InnerCommand  {
    @Override
    public void process(String msg) {
        System.out.println("aaaaaaaa");
    }
}

5.調用
代碼如下：

public static void main(String[] args) {
    InnerCommand instance = InnerCommandContext.getInstance(":admin");
    instance.process(":admin");
}