jvmgo

看了《自己动手写Java虚拟机》这本书

然后用go语言写了一个Java虚拟机

来试试看它能执行哪些Java代码吧

编译器：jdk1.8 虚拟机：jvmgo

public class Main {

// 手写双向循环链表
    public static void main(String[] args) {
        DoubleCircularLinkedList L = new DoubleCircularLinkedList();
        L.add(0,0);
        L.add(1,1);
        L.add(2,2);
        L.add(3);

L.show();

L.delete(1);
        L.show();

L.set(2,19);
        L.show();
    }

static class DoubleCircularLinkedList {
        // 头节点只做标识作用，不存放数据
        Node head;
        // 当前节点，用来更快地进行指定位置的插入删除操作
        Node pointer;
        // 当前节点所在的下标
        int pointerIndex;
        // 节点个数
        public int size;

public DoubleCircularLinkedList() {
            head = new Node();

head.setNext(head);
            head.setPrev(head);

pointer = head;
            pointerIndex = -1;
            size = 0;
        }

/**
            * 把pointer定位到index
            */
        public int indexTo(int index) {
            if (index < -1 || index > size - 1) {
                throw new ArrayIndexOutOfBoundsException("越界");
            } else {
                if (index == -1) {
                    pointer = head;
                    pointerIndex = -1;
                    return -1;
                } else if (index == pointerIndex) {
                    return pointerIndex;
                } else {
                    // 为了更高的效率，根据原来的位置与现在要定位的位置来改变，而不是每次都从头开始
                    // 向后走效率更高
                    while (index - pointerIndex > pointerIndex - index) {
                        pointer = pointer.getNext();
                        pointerIndex++;
                    }
                    while (index - pointerIndex < pointerIndex - index) {
                        pointer = pointer.getPrev();
                        pointerIndex--;
                    }
                    return pointerIndex;

}
            }
        }

/**
            * 在指定位置添加元素
            */
        public void add(int index, int data) {
            // 先让当前指针指向前一个位置
            indexTo(index - 1);

Node target = new Node(data);
            target.setNext(pointer.getNext());
            pointer.setNext(target);
            target.setPrev(pointer);
            target.getNext().setPrev(target);

size++;
        }

/**
            * 在末尾添加元素
            */
        public void add(int data) {
            pointer = head.getPrev();
            pointerIndex = size - 1;
            Node node = new Node(data);

pointer.getNext().setPrev(node);
            node.setNext(pointer.getNext());
            node.setPrev(pointer);
            pointer.setNext(node);

size++;
        }

/**
            * 在指定位置删除元素
            */
        public void delete(int index) {
            indexTo(index - 1);
            pointer.getNext().getNext().setPrev(pointer);
            pointer.setNext(pointer.getNext().getNext());
            size--;
        }

/**
            * 在末尾删除元素
            */
        public void delete() {
            indexTo(size - 2);
            pointer.getNext().getNext().setPrev(pointer);
            pointer.setNext(pointer.getNext().getNext());
            size--;
        }

public void set(int index, int data) {
            indexTo(index);
            pointer.setData(data);
        }

// 得到最后一个节点的数据
        public int get() {
            pointer = head.getPrev();
            pointerIndex = size - 1;
            return pointer.getData();
        }

//查看链表的全部元素
        public void show() {
            if (size == 0) {
                System.out.println("链表是空的");
            } else {
                int x = size;
                pointer = head;
                pointerIndex = -1;
                while (x-- != 0) {
                    System.out.println(pointer.getNext().getData());
                    pointer = pointer.getNext();
                    pointerIndex++;
                }
                System.out.println("================");
            }
        }
    }

static class Node {

private Node prev;
        private Node next;
        private int data;

Node(){}

Node(int data){
            this.data = data;
        }

Node(Node node){
            this.setNext(node.getNext());
            this.setPrev(node.getPrev());
            this.setData(node.getData());
        }

public Node getPrev() {
            return prev;
        }

public void setPrev(Node prev) {
            this.prev = prev;
        }

public Node getNext() {
            return next;
        }

public void setNext(Node next) {
            this.next = next;
        }

public int getData() {
            return data;
        }

public void setData(int data) {
            this.data = data;
        }
    }
}