Do apt-get update before install

Otherwise install may fail if the index is out of date.

week1/00-tools-setup.md

@@ -12,7 +12,7 @@ assignment submission system working for your account.
 #### On Ubuntu and Debian
 
 ```shell
-sudo apt-get install openjdk-8-jdk
+sudo apt-get update && sudo apt-get install openjdk-8-jdk
 sudo update-java-alternatives --set /usr/lib/jvm/java-1.8.0-openjdk-amd64
 ```
 
@@ -125,7 +125,7 @@ To submit assignments, you will need an SSH key. If you don't already have one,
 #### Ubuntu and Debian
 
 ```shell
-sudo apt-get install openssh-client
+sudo apt-get update && sudo apt-get install openssh-client
 ```
 
 #### macOS