The Java® Virtual Machine Specification, Java SE 7 Edition, Third Edition

3.10. Compiling Switches

Compilation of switch statements uses the tableswitch and lookupswitch instructions. The tableswitch instruction is used when the cases of the switch can be efficiently represented as indices into a table of target offsets. The default target of the switch is used if the value of the expression of the switch falls outside the range of valid indices. For instance:

int chooseNear(int i) {    switch (i) {        case 0:  return  0;        case 1:  return  1;        case 2:  return  2;        default: return -1;    }}

compiles to:

Method int chooseNear(int)0   iload_1             // Push local variable 1 (argument i)1   tableswitch 0 to 2: // Valid indices are 0 through 2      0: 28             // If i is 0, continue at 28 ...