An operand stack holds intermediate values used by bytecode operations in a Java virtual machine method invocation. Each stack frame has its own last-in-first-out operand stack, initially empty; its maximum depth is recorded in the class file. Values can be loaded from local variables, consumed by operations and replaced by results.[ref]
Starting from an empty operand stack,
iconst_2; iconst_3; iadd produces the successive contents 2, 2,3 and 5, with the top shown at the right. The addition consumes both operands. This abstract execution rule does not require a physical memory push for each operation: just-in-time compilation may retain values in processor registers while preserving the specified behavior. New to topics? Read the docs here!