After installing ubuntu, the restart is stuck on the startup animation screen. Change the quiet splash to quiet splash nomodeset to solve the problem. However, after entering the system and configuring the software, restart the system and find that the splash screen keeps flashing after the boot screen is skipped. I want to enter from the recovery mode. The system can't be entered, and it keeps flashing. Some posts on the Internet say that it is a graphics card problem, but the graphics card is no problem. It is not a graphics card problem when it gets stuck twice. Later, I saw that it was caused by the configuration of the JDK environment variables.
Resolution process:
1. I press "e" on the startup selection screen to enter the startup editing mode, change quiet splash to quiet splash text, and then press F10 to enter the system.
2. Then I commented out the JDK configuration, and the restart still has a splash screen problem
3. Later I tried to modify /etc/default/grub:
把 GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset"
改为 GRUB_CMDLINE_LINUX_DEFAULT="quiet splash text"，
Then update the boot with sudo update-grub
Then it can start successfully