比较两个有序集合

运用场景（交易所深度增量推送）

1. [[411.8,6],[411.75,11],[411.6,22],[411.5,9],[411.3,16]]
2. [[411.8,5],[411.7,11],[411.5,22],[411.5,9],[411.3,1]]

import java.util.ArrayList;
import java.util.List;

public class two {

    public static void main(String[] args) {

        /**
         * 两个集合是有序的，从大到小的
         * 
         * 1）.集合now有集合old没有的 ，添加
         * 
         * 2）.集合now有集合old有的的 ，舍弃
         * 
         * 3）.集合now没有但是集合old有的 ，数量标志位0
         * 
         * 4）.集合now有集合old也有的 但是数量不一致的 变更
         */

        //String[] 长度为2 第一个数据为价格，第二个数据为数量
        List<String[]> now = new ArrayList<String[]>();
        List<String[]> old = new ArrayList<String[]>();

        StringBuilder data = new StringBuilder();// 用于拼接最后的数据
        int oldSize = old.size();
        int nowSize = now.size();
        int index = 0; // now 集合索引
        int last_index = 0;// old 集合索引
        for (int i = 0, size = oldSize + nowSize; i < size; i++) {
            if (last_index >= oldSize && index >= nowSize) {//如果两个数据的每个元素都一致
                break;
            }
            double price = -1d;
            String amount = "";
            if (index < nowSize) { 
                price = Double.parseDouble(now.get(index)[0]);
                amount = now.get(index)[1];
            }
            double lastPrice = -1d;
            String lastAmount = "";
            if (last_index < oldSize) {
                lastPrice = Double.parseDouble(old.get(last_index)[0]);
                lastAmount = old.get(last_index)[1];
            }

            if (price == lastPrice) {
                if (!amount.equals(lastAmount)) {
                    data.append("[" + price + "," + amount + "],");
                }
                last_index++;
                index++;
            } else if (price > lastPrice) {
                data.append("[" + price + "," + amount + "],");
                index++;
            } else if (price < lastPrice) {
                data.append("[" + price + "," + 0 + "],");
                last_index++;
            }

        }

    }
}