The || symbol in java and in all the C family or programming languages is used to signify "or" in a condition.
For example you want to invoke a particular method if either one of 2 condition occurs. So you would type:
if(condition 1 || condition 2).
If either of these condition is upheld then the method would be invoked.
In contrast, you have the && which is used to symbolise "and"
so you would have:
if(condition 1 && condition 2)
the method would be invoked only if both of these conditions is upheld. If one of them is not then the method would not be invoked.