这个方法很多文章都有，比如eclipse Installed JREs 添加 jdk9时，提示“Target is not a JDK root. System library was not found.”_有一种人仅仅是认识就很好了的博客-CSDN博客_eclipse installed jres1.进入eclipse->help->install new software->输入网址 : http://download.eclipse.org/eclipse/updates/4.7-U-builds去掉下面的Group item by category 再在地址栏回车，在显示的内容中找到eclipse sdk 勾选，点击next:然后会下载这个jdk 需要等待一段时间https://blog.csdn.net/qq_36350532/article/details/79039262?spm=1001.2101.3001.6650.5&utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromBaidu%7ERate-5.pc_relevant_default&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromBaidu%7ERate-5.pc_relevant_default&utm_relevant_index=10这里想写的备注是原有下载地址无法访问了，可以将地址改成这个
https://download.eclipse.org/eclipse/update/4.22
