错误:无法访问包 org.apache.commons [英] Error: The package org.apache.commons is not accessible

问题描述

我最近才开始使用 Eclipse，但在尝试安装外部库时遇到了问题.按照在线教程，我将 .jar 文件添加到类路径，并在引用的库文件夹中看到它.尽管如此，在尝试导入时，出现错误:

I have just recently started using Eclipse and am running into problems trying to install external libraries. Following online tutorials, I add the .jar file to the classpath and I see it in the referenced libraries folder. Despite this, when trying to import, I get the error:

无法访问包 org.apache.commons

The package org.apache.commons is not accessible

作为参考，我正在尝试安装 apache math commons 库.

For reference, I am trying to install the apache math commons library.

推荐答案

你的代码可能有两个问题.

Your code probably has two issues.

首先，import 语句是错误的，因为在 Java 中你不能添加包本身，但包的所有类如下(注意 .*; 最后):

First, the import statement is wrong since in Java you cannot add a package itself, but all classes of a package as follows (note .*; at the end):

import org.apache.commons.math4.linear.*;

或特定的类，例如

import org.apache.commons.math4.linear.FieldMatrix;

其次，您使用 Java 平台模块系统 (JPMS)>module-info.java 文件在默认包中可能没有必需的 requires ; 语句.JPMS 是在 Java 9 中引入的，你有 Java 12.

Second, you use the Java Platform Module System (JPMS) by having a module-info.java file in the default package probably without the required requires <module>; statement. JPMS was introduced in Java 9 and you have Java 12.

执行以下操作之一:

• 删除module-info.java文件(如果需要，您可以通过右键单击项目文件夹并选择配置>创建模块来重新创建它-info.java)
• 在module-info.java添加对应的requires语句，例如通过转到带有 import 语句的行并使用相应的 Quick Fix (Ctrl+1)

• Delete the module-info.java file (if needed, you can recreate it via right-clicking the project folder and choosing Configure > Create module-info.java)
• In module-info.java add the corresponding requires statement, e.g. by going to the line with the import statement and using the corresponding Quick Fix (Ctrl+1)

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