Java: what makes two keys equal in a hashmap?








You need to override two methods in key class:
public int hashCode();
public boolean equals(Object o);



List the files opened by a specific program/process








1. find the pid, i.e. process id, of the program/application. e.g. java
ps aux | grep java
2. use lsof to list the files opened by that process (where 13317 is the pid, e.g.).
lsof -p 13317

See Also: http://www.cyberciti.biz/faq/howto-linux-get-list-of-open-files/


Picasa for Linux could not start








  1. Dowload: http://picasa.google.com/linux/
  2. Install: sudo dpkg -i picasa_2.7.3736-15_i386.deb
  3. Could not start?
    /usr/bin/picasa: line 139:  6750 Segmentation fault      "$PIC_BINDIR"/wrapper check_dir.exe.so
    /usr/bin/picasa: line 175:  6845 Segmentation fault      "$PIC_BINDIR/wrapper" regedit /E $registry_export HKEY_USERS\\S-1-5-4\\Software\\Google\\Picasa\\Picasa2\\Preferences\\
    

    Fix: sudo sysctl -w vm.mmap_min_addr=0; rm -fr ~/.picasa



Dell Vostro V13: Turn on/off charging








Fn + F2


Merge PDF files into one








gs -q -sPAPERSIZE=letter -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=out.pdf in1.pdf in2.pdf in3.pdf