Cause-There is no src.zip file in the jdk directory
Solution:
1. Download scr.zip
Link: https://pan.baidu.com/s/1peLRPvORislqGb3M4u_geQ
extraction code: hhmz
2. Copy the downloaded scr.zip to jdk / lib folder
3. Select the code you want to view the source code in eclipse, click f3, source not found is displayed again, click the red box
4. Click the red box again
5. Select scr.zip in the root directory of jdk / lib