Mainly because the size and scope of storage space are different. The following is the storage space of JAVA's basic type byte: 1 byte, 2 bytes in the range of-128~ 127short, and 4 bytes in the range of -2,15th power ~2,15th power-/kloc-0. The storage space of -2' s 3 1 power to -2' s 3 1 power Long is 8 bytes, and the default values of -2 to-1 to 63' s power are all upstairs. If int is in C and C++, it may be 2 bytes. This must be made clear! Please don't refer to this answer, pay attention to your character.