First things first: it's unlikely you've stumbled across a Java bug. Blame your code first.
08120
is an octal literal in Java since it starts with a leading zero.
And 8 is not a valid octal digit (only 0 to 7 are).
Therefore you get a compilation error, albeit a little misleading.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…