如何从ArrayList＃toString（）中删除括号[]？ [英] How to remove the brackets [ ] from ArrayList#toString()?

问题描述

我在Java中创建了一个如下所示的数组列表：

I have created an Array List in Java that looks something like this:

 public static ArrayList<Integer> error = new ArrayList<>();

for (int x= 1; x<10; x++)
 { 
    errors.add(x);
 }

当我打印错误时我得到错误

When I print errors I get it errors as

[1,2,3,4,5,6,7,8,9]

[1,2,3,4,5,6,7,8,9]

现在我要从此数组列表中删除方括号（[]）。我以为我可以使用方法errors.remove（[），但后来我发现它只是布尔值并显示true或false。有人可以建议我怎么做到这一点？

Now I want to remove the brackets([ ]) from this array list. I thought I could use the method errors.remove("["), but then I discovered that it is just boolean and displays a true or false. Could somebody suggest how can I achieve this?

提前感谢你的帮助。

推荐答案

你是可能会调用系统。 out.println 打印列表。 JavaDoc说：

You are probably calling System.out.println to print the list. The JavaDoc says:

This method calls at first String.valueOf(x) to get the printed object's string value

括号由ArrayList的 toString 实现添加。要删除它们，您必须先获取字符串：

The brackets are added by the toString implementation of ArrayList. To remove them, you have to first get the String:

String errorDisplay = errors.toString();

然后删除括号，如下所示：

and then strip the brackets, something like this:

errorDisplay = errorDisplay.substring(1, errorDisplay.length() - 1);

依赖 toString（）实施。 toString（）仅用于生成用于记录或调试目的的人类可读表示。所以最好在迭代时自己构建String：

It is not good practice to depend on a toString() implementation. toString() is intended only to generate a human readable representation for logging or debugging purposes. So it is better to build the String yourself whilst iterating:

List<Integer> errors = new ArrayList<>();
StringBuilder sb = new StringBuilder();
for (int x = 1; x<10; x++) { 
    errors.add(x);
    sb.append(x).append(",");
}
sb.setLength(sb.length() - 1);
String errorDisplay = sb.toString();

请注意，这不是一个数组，只是一个显示列表内容的String。要从列表创建数组，可以使用 list.toArray（）：

Note that this is not an array, just a String displaying the contents of the list. To create an array from a list you can use list.toArray():

// create a new array with the same size as the list
Integer[] errorsArray = new Integer[errors.size()];
// fill the array
errors.toArray(errorsArray );

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