What's the difference between java bytecode astore_1 and astore_2 ?
The instructions astore_n, for small values of n, are just shorthand equivalents for astore n. Either version stores what's on top of the stack into local variable n.
astore_1 is the same as astore 1, and astore_2 is the same as astore 2, except that astore_1 and astore_2 are one byte each, whereas astore is a two-byte instruction.
来源：https://stackoverflow.com/questions/6983641/whats-the-difference-between-java-bytecode-astore-1-and-astore-2