Java I/O - If Stream Contain Nothing Then Close It

For every stream that we create for java i/o we write at the end in finally block

finally
{
if(is!=null)
{
is.close();
}
}

It works

my question is as per syntax in if (is!=null) this means that if is means stream contain some value then close it(!=null)

then how it in my opnion it should be like (in logical way)

if stream contain nothing then close it

if(is==null)
{
is.close();
}

I am confuse about working this line