Java 中 eval() 解析器和二维数组的实现 [英] ImplementIon of eval() parser and 2d array in Java

问题描述

我一直在解决两个与 Java 相关的问题.一个简单，一个更难.

I have really stuck on two Java related issues. One simple and one more difficult.

关于创建一个二维数组，我像这样初始化一个表:

Regarding the creation of a 2D array, I initialize a table like this:

private String [][] table_of_classifiers = null;

然后，在一个函数中，我像这样填充它的内容:

and then, within a function, I fill its contents like this:

        String [][] table_of_classifiers = {
            {"x1","x","x","x","x"},
            {"x2","x","x","x","x"},
            {"x3","x","x","x","x"},
            {"x4","x","x","x","x"},
            {"x5","x","x","x","x"},
            {"x6","x","x","x","x"},
        };

但是您可以猜到第二个表会覆盖(本地)第一个表，这当然不是我想要做的.我做错了什么?注意表的维度一开始是不知道的.

But as you can guess the second table overwrites (locally) the first one, that is of course not what I want to do. What I do wrong? Note that the dimension of the table is not known from the beginning.

推荐答案

只需:

class Foo {
    private String [][] table_of_classifiers = null;

    void bar() {
        table_of_classifiers = new String[][] {
                    {"x1","x","x","x","x"},
                    {"x2","x","x","x","x"},
                    {"x3","x","x","x","x"},
                    {"x4","x","x","x","x"},
                    {"x5","x","x","x","x"},
                    {"x6","x","x","x","x"},
        };
    }
}

Java 没有 eval(因为它是一种编译语言)，但它有 反射.不过，这几乎肯定不是您想做的任何事情的最佳方法.

Java doesn't have eval (because it's a compiled language), but it does have reflection. It's almost certainly not the best approach to whatever it is that you want to do, though.

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