I'm trying to write a small script to change the current directory to my project directory:
Shell scripts are run inside a subshell, and each subshell has its own concept of what the current directory is. The
cd succeeds, but as soon as the subshell exits, you're back in the interactive shell and nothing ever changed there.
One way to get around this is to use an alias instead:
alias proj="cd /home/tree/projects/java"