Question

我了解到例外情况很慢：

但是这篇文章（http://blogs.atlassian.com/2011/05/if_you_use_exceptions_for_path_control_dont_fill_in_the_stac/）说我们可以使用Exception来模拟goto语句：

所以我认为编写这样的代码是可以的：

public class MyService {

    public Result service(int i) {
        Result result = new Result();
        try {

            Util.checkCommonArguments(i);

            //my business logic...
            if ((i % 2) != 0) {
                throw new BizException("002", "can not be odd");
            }
            if (i > 200) {
                throw new BizException("003", "can not be greater than 200");
            }

            // the normal processing...


            result.setCode("000");
            result.setDesc("ok");
        } catch (BizException e) {
            result.setCode(e.getCode());
            result.setDesc(e.getMessage());
        } catch (Exception e) {
            result.setCode("999");
            result.setDesc("system error");
        }
        return result;
    }


}

class Util {
    public static void checkCommonArguments(int input) {
        if (input < 0) {
            throw new BizException("001", "can not be negative.");
        }
        //maybe more
    }
}

class Result {

    private String code;
    private String desc;

    //getter and setter
}

class BizException extends RuntimeException {
    private String code;

    public BizException(String code, String message) {
        super(message);
        this.code = code;
    }
    @Override
    public Throwable fillInStackTrace()
    {
        return this;
    }
}

但是不要填写堆栈跟踪＆＃39;不起作用：

// throw but catch, but not Filling in exception stack traces 
public void method5(int i) {
    try {
        value = ((value + i) / i) << 1;
        // i & 1 is equally fast to calculate as i & 0xFFFFFFF; it is both
        // an AND operation between two integers. The size of the number plays
        // no role. AND on 32 BIT always ANDs all 32 bits
        if ((i & 0x1) == 1) {
            throw new MyBizException();
        }
    } catch (MyBizException e) {
        //maybe do something
    }
}

method5's cost time is almost the same as:

    // This one will regularly throw one
public void method3(int i) throws Exception {
    value = ((value + i) / i) << 1;
    // i & 1 is equally fast to calculate as i & 0xFFFFFFF; it is both
    // an AND operation between two integers. The size of the number plays
    // no role. AND on 32 BIT always ANDs all 32 bits
    if ((i & 0x1) == 1) {
        throw new Exception();
    }
}

现在我很困惑。一方面，我希望我的代码干净清晰（就像课程＆＃39; MyService＆＃39;）。另一方面，Exception真的很慢。

我应该使用Exception来模拟goto语句吗？感谢。

Answer 1

不要在正常的程序流程中使用异常。它们用于超出开发人员控制范围的特殊情况。它们速度慢，效率低，专为错误处理而设计，而非业务逻辑。

在今天的开发环境中，刺激goto是一个糟糕的设计决定。他们很容易跟随，难以维护。重构代码以改为使用中断或其他控制逻辑。

Answer 2

使用异常进行流量控制既不符合良好的设计，也不符合效率。这至少会产生不必要的对象。我鼓励你看一下Joshua Bloch的“Effective Java”，它明确地涵盖了这个topic。

我应该使用Exception来模拟java中的goto语句

2 个答案: