StackMachine implementation using this tutorial: http://gameprogrammingpatterns.com/bytecode.html

StackMachine.java

import java.util.Stack;

/* Based on http://gameprogrammingpatterns.com/bytecode.html */
public class StackMachine
{
    public final int INST_LITERAL = 0;
    public final int SET_HEALTH = 1;
    public final int INST_GET_HEALTH = 2;
    private static final int INST_ADD = 3;

    public Stack<Integer> stack;

    /*
    LITERAL 0    [0]            # Wizard index
    LITERAL 0    [0, 0]         # Wizard index
    GET_HEALTH   [0, 45]        # getHealth()
    LITERAL 5    [0, 45, 5]     # Add bonus health amount
    ADD          [0, 50]        # Add bonus health (5) to health
    SET_HEALTH   []             # Set health to result
     */
    public int[] instructions = { INST_LITERAL, 0, INST_LITERAL, 0, INST_GET_HEALTH, INST_LITERAL, 5, INST_ADD, SET_HEALTH};

    private int pointer;

    public void run()
    {
        stack = new Stack();
        pointer = -1;
        while (pointer < instructions.length - 1)
        {
            handleInstruction(instructions[++pointer]);
        }
    }

    private void handleInstruction(int command)
    {
        switch (command)
        {
            case INST_LITERAL:
                int value = instructions[++pointer];
                stack.push(value);
                break;
            case INST_GET_HEALTH:
            {
                int wizard = stack.pop();
                stack.push(getHealth(wizard));
                break;
            }
            case SET_HEALTH:
                int health = stack.pop();
                int wizard = stack.pop();
                setHealth(wizard, health);
                break;
            case INST_ADD:
                int b = stack.pop();
                int a = stack.pop();
                stack.push(a + b);
                break;
        }
    }

    private Integer getHealth(int wizard) {
        return 45;
    }

    private void setHealth(int wizard, int health)
    {
        System.out.println("Wizard " + wizard + " health set to " + health);
    }
}