It depends on how you install it
It can be installed in any directory
Usually operation and maintenance will have installation and deployment specifications, which shall prevail

which java look where you clicked

It depends on which method you use to install it
Under Ubuntu, directly apt-get的话jdk目录在/usr/lib/jvm/下(因此个人推荐安在这), 这种情况下which java看到的是软链接的路径, 不是真正的jdkdirectly locate the directory

I downloaded the tar package myself, unzipped it directly under my home directory, and then configured it .bashrc under

export JAVA_HOME=/home/xxx/jdk
export $PATH=$PATH:$JAVA_HOME/bin