我在Debian上，已经安装了OpenJDK 8以及包openjdk-8-doc和default-jdk-doc;但是，每当我为JDK 8 API实用程序指定类或程序包名称时，我都无法查看javadoc类的任何文档，该实用程序无法显示文档引发以下错误：
ArrayList案例：
kais@debian:~$ javadoc ArrayList
Loading source files for package ArrayList...
javadoc: warning - No source files for package ArrayList
Constructing Javadoc information...
javadoc: warning - No source files for package ArrayList
javadoc: error - No public or protected classes found to document.
1 error
2 warnings
kais@debian:~$ javadoc java.lang.ArrayList
Loading source files for package java.lang.ArrayList...
javadoc: warning - No source files for package java.lang.ArrayList
Constructing Javadoc information...
javadoc: warning - No source files for package java.lang.ArrayList
javadoc: error - No public or protected classes found to document.
1 error
2 warnings
JPanel案例：
kais@debian:~$ javadoc JPanel
Loading source files for package JPanel...
javadoc: warning - No source files for package JPanel
Constructing Javadoc information...
javadoc: warning - No source files for package JPanel
javadoc: error - No public or protected classes found to document.
1 error
2 warnings
kais@debian:~$ javadoc javax.swing.JPanel
Loading source files for package javax.swing.JPanel...
javadoc: warning - No source files for package javax.swing.JPanel
Constructing Javadoc information...
javadoc: warning - No source files for package javax.swing.JPanel
javadoc: error - No public or protected classes found to document.
1 error
2 warnings
kais@debian:~$ javadoc javax.swing
Loading source files for package javax.swing...
javadoc: warning - No source files for package javax.swing
Constructing Javadoc information...
javadoc: warning - No source files for package javax.swing
javadoc: error - No public or protected classes found to document.
1 error
2 warnings
这在我看来很奇怪，因为已安装的软件包openjdk-8-doc应该包含javadoc所需的文档。
有什么想法吗？