Java isEmpty() 未为字符串定义？
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Java isEmpty() undefined for String?
提问by Aaron Moodie
I'm working on a school project in eclipse, and when I try and use the isEmpty()method on a String, Eclipse shows up the following error:
我正在 eclipse 中处理一个学校项目，当我尝试isEmpty()在 a 上使用该方法时String，Eclipse 显示以下错误：
The method isEmpty() is undefined for the type String
方法 isEmpty() 未定义为 String 类型
I've run the Java updates, but am still getting it. Is any reason why this method would be undefined?
我已经运行了 Java 更新，但仍然得到它。是否有任何原因未定义此方法？
采纳答案by Rich Seller
String.isEmpty() was added in Java 6. In earlier versions you can use StringUtils.isEmpty(String)from Apache's commons-langlibrary.
String.isEmpty() 是在Java 6中添加的。在早期版本中，您可以使用StringUtils.isEmpty(String)从Apache的公地郎库。
To configure Eclipse to use the 1.6 JRE, go to Window->Preferences->Java->Installed JREs. If you haven't already got JAva 1.6 configured, select Add...,browse to your 1.6 installation and add it.
要将 Eclipse 配置为使用 1.6 JRE，请转至 Window->Preferences->Java->Installed JREs。如果您还没有配置 JAva 1.6，请选择Add...，浏览到您的 1.6 安装并添加它。
(source: lumidant.com)
（来源：lumidant.com）
回答by Jonik
String.isEmpty()was introduced in Java release 1.6. You might want to check what JDK version you're using for your project. (I don't know much about Eclipse myself, but it should be somewhere in the project settings.)
String.isEmpty()在 Java 1.6 版中引入。您可能想要检查您的项目使用的 JDK 版本。（我自己对 Eclipse 不太了解，但它应该在项目设置中的某个地方。）
回答by dogbane
If you're not on Java 6, String.length() == 0 will return the same result as String.isEmpty().
如果您使用的不是 Java 6，则 String.length() == 0 将返回与 String.isEmpty() 相同的结果。
回答by jlplayel
I had this problem in a big project where all previous set-up were with Java 8 (general and project level compiler settings). The solution was to move to the top The "JRE System Library[jre1.8.0]" in the "Order and Export" tab in Build Path of the affected project.
我在一个大项目中遇到了这个问题，其中所有以前的设置都是使用 Java 8（通用和项目级编译器设置）。解决方案是将受影响项目的Build Path中的“Order and Export”选项卡中的“JRE System Library[jre1.8.0]”移至顶部。
