hashmap简单实例（个人使用经验）

一、HashMap<int,String>是错误的：因为int是基本类型，而key和value要求是对象，所以要用Integer而不是int。HashMap<String,Object>的value一定要是Object类型。

二、HashMap<>同一元素添加二次覆盖

HashMap test = new HashMap<Integer, String>();

test.put(1, "i");

test.put(2, "you");

test.put(3, "she");

test.put(3, "he");

那么，test.size是3，而key为3所对应的value为he。

三、hashmap综合应用实例：

文件region_template基本地域数据，从geoip.txt的ip映射的地域数据中提取省、市信息，补充到region_template后面输出到新文件region_template_analytic。

代码如下：

importjava.io.*;

importjava.util.HashMap;

import java.io.BufferedReader;

importjava.io.BufferedWriter;

importjava.io.File;

importjava.io.FileInputStream;

importjava.io.FileNotFoundException;

importjava.io.FileOutputStream;

importjava.io.IOException;

importjava.io.InputStreamReader;

import java.io.OutputStreamWriter;

importjava.util.ArrayList;

importjava.util.Iterator;

importjava.util.List;

importjava.util.Set;

importjava.util.Vector;

importcom.vpon.wizad.etl.util.Region;

public classmappingToRegion_template {

private HashMap<String, Region>myRegionTemplates;

private HashMap<String, Region>RegionAnalytic;

public mappingToRegion_template(StringregionFile)

throwsUnsupportedEncodingException, FileNotFoundException {

this.myRegionTemplates = newHashMap<String, Region>();

this.RegionAnalytic = newHashMap<String, Region>();

File allRegion = newFile(regionFile);

BufferedReader br = null;

String line = "";

String cvsSplitBy =",";

if (allRegion == null)

System.out.println("nofile of" + regionFile);

else {

try {

br = newBufferedReader(new InputStreamReader(new FileInputStream(regionFile),"utf-8"));

while((line = br.readLine()) != null) {

//Skip empty lines.

if(line.matches("^[\\n\\s]+$")) {

continue;

}

String[]row = line.split(cvsSplitBy);

//                                           System.out.println(line.toString());

StringregionID = row[0];

StringregionName = row[1];

booleancountry = false;

booleanprovince = false;

intcityLevel = 0;

if(row[2].equals("1")) {

country= true;

}

if(row[3].equals("1")) {

province= true;

}

try{

cityLevel= Integer.parseInt(row[4]);

}catch (Exception e) {

cityLevel= 0;

}

StringparentRegionID = row[5];

if(!parentRegionID.matches("\\d+")) {

parentRegionID= null;

}

//                                           if(regionName.matches("^包")){

//                                           System.out.println(regionName);

//

//                                  }

if(regionName.matches("(.*)(市|省)$")){//thesame as "(.*)[市省]$"

//if(regionName.endsWith("省")|regionName.endsWith("市")){

regionName= regionName.substring(0, regionName.length()-1);

}elseif( regionName.matches("(.*)(区)$") )

{

if(regionName.startsWith("内蒙古")){

regionName= regionName.substring(0,3);

}else{

regionName= regionName.substring(0,2);

}

//                                                     System.out.println(regionName);

}

Regionregion = new Region(regionID, regionName, country,province, cityLevel,parentRegionID);

//                                           System.out.println(region.getName());

if(this.myRegionTemplates.containsKey(regionName))

System.out.println(regionName);

this.myRegionTemplates.put(regionName,region);

this.RegionAnalytic.put(regionID,region);

}

} catch (FileNotFoundExceptione) {

e.printStackTrace();

} catch (IOExceptione) {

e.printStackTrace();

} finally {

if (br !=null) {

try{

br.close();

}catch (IOException e) {

e.printStackTrace();

}

}

}

}

//               吉林处理后的问题，少了

System.out.println(this.myRegionTemplates.size());

System.out.println(this.RegionAnalytic.size());

}

private void mapADAssociation(StringgeoipFile) throws IOException

{

System.out.println("pid:"+this.myRegionTemplates.get("吉林").getRegionID());

int regionNumber =this.RegionAnalytic.size();

BufferedReader br = null;

String line = "";

String FilesplitBy ="\t";

try{

br = newBufferedReader(new InputStreamReader(new FileInputStream(

geoipFile),"utf-8"));

while ((line =br.readLine()) != null) {

// Skipempty lines.

if(line.matches("^[\\n\\s]+$")) {

continue;

}

String[]row = line.split(FilesplitBy);

Stringgeoip_province = row[2];

Stringgeoip_city = row[3];

//city isnull: prosses as province

if(geoip_city == null) {

if(geoip_province == null) {

thrownew RuntimeException("province and city are both null");

}else{

geoip_city= geoip_province;

}

}

//System.out.println(geoip_province+","+geoip_city);

if(geoip_province.matches("国外"))

continue;

if(geoip_province == geoip_city) {

if(this.myRegionTemplates.containsKey(geoip_province)) {

continue;

}else {

System.out.println(geoip_province);

thrownew RuntimeException("illegal province: no that " + geoip_province);

}

} else {

if(this.myRegionTemplates.containsKey(geoip_city)){

continue;

}else{

//                                                     System.out.println(geoip_province+","+geoip_city);

RegionparentRegion = this.myRegionTemplates.get(geoip_province);

StringparentRegionID= parentRegion.getRegionID();

booleancountry = false;

booleanprovince = false;

int cityLevel = 0;

String regionID =Integer.toString(++regionNumber);

Region region = new Region(regionID,geoip_city, country, province, 0, parentRegionID);

//                         this.myRegionTemplates.put(geoip_city, region);

this.RegionAnalytic.put(regionID,region);

}

}

}

} catch (RuntimeException e){

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

} finally {

if (br != null) {

try {

br.close();

} catch(IOException e) {

e.printStackTrace();

}

}

}

}

private void writeToFile(StringoutputFile) throws IOException {

File file = newFile(outputFile);

if(!file.exists())

file.createNewFile();

FileOutputStream out=newFileOutputStream(file,true);

System.out.println(this.myRegionTemplates.size());

System.out.println(this.RegionAnalytic.size());

for(int i = 1; i <=this.RegionAnalytic.size(); i++)

{

Region outRegion =this.RegionAnalytic.get(Integer.toString(i));

int isCountry = outRegion.isCountry()?1:0;

int isProvince =outRegion.isProvince()?1:0;

StringBuffer sb =new StringBuffer(outRegion.getRegionID()+","+outRegion.getName()

+","+isCountry+","+isProvince+","+outRegion.getCityLevel()+","+outRegion.getParentRegionID()+"\n");

//                         StringBuffer sb=newStringBuffer(outRegion.toString());

out.write(sb.toString().getBytes("utf-8"));

}

}

public static void main(String[] args)throws Exception {

String regionFile = "F:/region_template/region_template";

String geoipFile ="F:/geoip.txt";

String outputFile ="F:/region_template_analytic/region_template_analytic";

mappingToRegion_template db =new mappingToRegion_template(regionFile);

db.mapADAssociation(geoipFile);

db.writeToFile(outputFile);

}

}