Java中数组中的命令行参数

command line arguments in array in Java

提问by user2711992

I am a very beginner in Java, I have a question regarding to use command line arguments line in array, for example, I tried to type:

我是 Java 的初学者，我有一个关于在数组中使用命令行参数行的问题，例如，我尝试输入：

double []a=Double.parseDouble(args[0]);

however, it said" cannot convert double to double",I cannot figure out it, as I can do

但是，它说“无法将双倍转换为双倍”，我无法弄清楚，因为我可以做到

double a=Double.parseDouble(args[0]);

so what is wrong with using CL arguments input in array then?Thanks

那么在数组中使用 CL 参数输入有什么问题呢？谢谢

采纳答案by arshajii

Simply, Double.parseDouble()returns a doubleas opposed to a double[], so you can't assign it to a variable of type double[].

简单地说，Double.parseDouble()返回 adouble而不是 a double[]，因此您不能将其分配给类型为 的变量double[]。

If you want to convert all of the strings in argsto doubles, you could try something like

如果要将所有字符串转换args为doubles，可以尝试类似

double[] a = new double[args.length];
for (int i = 0; i < args.length; i++) {
    a[i] = Double.parseDouble(args[i]);
}

Of course, if you just want args[0], then store the parsed doubleas you are doing in your second snippet; not much sense in using an array in this case.

当然，如果您只是想要args[0]，则将解析后的内容存储double在您的第二个代码段中；在这种情况下使用数组没有多大意义。

回答by xagyg

It must be an array that is assigned...

它必须是一个分配的数组...

e.g.

例如

double[] a = new double[] { Double.parseDouble(args[0]) };

回答by Stephen C

however, it said" cannot convert double to double",I cannot figure out it, as I can do

但是，它说“无法将双倍转换为双倍”，我无法弄清楚，因为我可以做到

What it actuallysaid was "cannot convert doubleto double[]". The []is crucial to the meaning of the error message ... and you shouldn't ignore it.

它实际上说的是“无法转换double为double[]”。的[]是错误信息的意义至关重要......你不应该忽略它。

It is telling you that you cannot treat a doubleas an array of double.

它告诉您不能将 adouble视为double.

---

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If you want to initialize a double[], you need to allocate a doublearray first; e.g.

如果要初始化 a double[]，需要先分配一个double数组；例如

double [] a = new double[1];
a[0] = Double.parseDouble(args[0]);

Or you could do that in one statement:

或者你可以在一个声明中做到这一点：

double [] a = new double[]{Double.parseDouble(args[0])};

or even

甚至

double [] a = {Double.parseDouble(args[0])};