TreeMap学习笔记（一）

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package com.qunar.yuliang.test13;import com.google.common.base.Charsets;import com.google.common.io.Files;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import java.io.File;import java.io.IOException;import java.util.Iterator;import java.util.List;import java.util.TreeMap;/** * Created by yuliang.jin on 14-7-9. */public class HotelInfoSorter {    private static Logger logger = LoggerFactory.getLogger(HotelInfoSorter.class);    public static File getFileSortedByHotelCode(File hotelInfoFile) throws IOException {        TreeMap<String, String> hotelInfo = new TreeMap<String, String>();        List<String> lines = Files.readLines(hotelInfoFile, Charsets.UTF_8);        int size = lines.size();        String[][] hotelInfoParts = new String[size][];        /**         * split each item of hotel info into hotel code and hotel name, and put them into a tree map.         */        for (int i = 0; i < size; i++) {            hotelInfoParts[i] = lines.get(i).split("\\s+", 2);            hotelInfo.put(hotelInfoParts[i][0], hotelInfoParts[i][1]);            logger.info("酒店代号：" + hotelInfoParts[i][0]);            logger.info("酒店名称：" + hotelInfoParts[i][1]);        }        /**         * save the sorted info in the tree map to a file         */        File fileSortedByHotelCode = new File("src/main/resources/test13/fileSortedByHotelCode");        Iterator iterator = hotelInfo.keySet().iterator();        while (iterator.hasNext()) {            String hotelCode = (String) iterator.next();            String hotelName = hotelInfo.get(hotelCode);            Files.append(hotelCode + "\t" + hotelName + "\n", fileSortedByHotelCode, Charsets.UTF_8);        }        return fileSortedByHotelCode;    }}

遍历TreeMap：

Iterator iterator = hotelInfo.keySet().iterator();        while (iterator.hasNext()) {            String hotelCode = (String) iterator.next();            String hotelName = hotelInfo.get(hotelCode);            Files.append(hotelCode + "\t" + hotelName + "\n", fileSortedByHotelCode, Charsets.UTF_8);        }

按key逆序输出TreeMap的值：仅对keySet进行逆序。

        Iterator iterator = hotelInfo.keySet().iterator();        List<String> keyList = new LinkedList<String>();        while (iterator.hasNext()) {            String hotelCode = (String) iterator.next();            keyList.add(hotelCode);        }        Collections.reverse(keyList);        for(String hotelCode : keyList) {           Files.append(hotelCode + "\t" + hotelInfo.get(hotelCode) + "\n", fileSortedByHotelCode, Charsets.UTF_8);        }

总结：

1）遍历TreeMap：Iterator iterator = hotelInfo.keySet().iterator();

2）LinkedList逆序：Collections.reverse(keyList);

3）遍历LinkedList：for(String hotelCode : keyList) {}

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