I have a nested MAP. I want to save these Map in a text file and then use this file in another projects. I can save outerMap correctly, however I need an efficient code to load this file into same Maps (I use '#' to separating key of outerMap and its innerMap).
Map <String, Map <String,Double>> outerMap= new HashMap<>();
Map <String,Double> innerMap= new HashMap<>();
.
.
.
PrintWriter writer = new PrintWriter("e:\\t.txt", "UTF-8");
Iterator it = outerMap.entrySet().iterator();
while (it.hasNext()) {
Map.Entry pairs = (Map.Entry)it.next();
writer.println(pairs.getKey() + "#" + pairs.getValue());
}
writer.close();
On your question in comment:
Gson gson = new Gson();
Map<String, Map<String, Double>> outerMap = new HashMap<>();
Map<String, Double> innerMap = new HashMap<>();
innerMap.put("1", 1.0);
innerMap.put("2", 2.0);
outerMap.put("key1", innerMap);
String json = gson.toJson(outerMap);
Path path = FileSystems.getDefault().getPath("", "myfile.txt");
Files.write(path, json.getBytes("UTF-8"), StandardOpenOption.CREATE, StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING);
json = new String(Files.readAllBytes(path));
outerMap = gson.fromJson(json, new TypeToken<Map<String, Map<String, Double>>>(){}.getType());
for (Map.Entry<String, Map<String, Double>> outerEntry: outerMap.entrySet()) {
System.out.println(outerEntry.getKey());
innerMap = outerEntry.getValue();
for (Map.Entry<String, Double> innerEntry: innerMap.entrySet()) {
System.out.println(" " + innerEntry.getKey() + "->" + innerEntry.getValue());
}
}
Output:
key1
2->2.0
1->1.0
You need use Gson library.
If you don't need human readable content in text-file, you can use approach, suggested in the first comment:
Map<String, Map<String, Double>> outerMap = new HashMap<>();
Map<String, Double> innerMap = new HashMap<>();
innerMap.put("1", 1.0);
innerMap.put("2", 2.0);
outerMap.put("key1", innerMap);
// write to file
try (ObjectOutput objectOutputStream = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream("myfile2.txt", false)))) {
objectOutputStream.writeObject(outerMap);
} catch (Throwable cause) {
cause.printStackTrace();
}
// read from file
try (ObjectInput objectInputStream = new ObjectInputStream(new BufferedInputStream(new FileInputStream("myfile2.txt")))) {
outerMap = (Map<String, Map<String, Double>>) objectInputStream.readObject();
} catch (Throwable cause) {
cause.printStackTrace();
}
You will have your Map on 'outerMap' reference.
This sounds pretty straightforward to me.
(Assuming you want to load the values of the file into innerMap)
FileInputStream inputStream = new FileInputStream("e:\\t.txt");
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
String buffer;
while((buffer = reader.readLine()) != null){
String[] pairs = buffer.split("#");
innerMap.put(pairs[0],Double.parseDouble(pairs[1]));
}
Pepper it with safety checks where you deem necessary.
NOTE : Sample code is written blindly and might be subject to careless mistakes.
Related
How to generate list of map into csv?
I try to get the key as headers and values as columns but, I get a list of values in the same key.
sample output
To generate a CSV file from a list of maps in Java, you can use a combination of the StringJoiner class and the FileWriter class.
StringJoiner sj = new StringJoiner(",");
for (Map<String, String> map : listOfMaps) {
for (Map.Entry<String, String> entry : map.entrySet()) {
sj.add(entry.getKey() + "=" + entry.getValue());
}
}
FileWriter fw = new FileWriter("output.csv");
fw.write(sj.toString());
fw.flush();
fw.close();
Issue adding a list from one hashmap's value to another's
Basically, I have 2 hashmaps (map1 and map2), both have the same keys(Integers from 0-500), but different values. What I'm wanting to do is use the value of map1, which is a String, as the key and the value of map2, which is a List, as the value. Adding map1 as the key is working, no problem, but when I try to add map2's value as map's value, it just returns as null.
This is for a homework project, where we are given 2 .csv files, one with labels and another with fake image file names, and have to be able to search by either image label or image file name.
Map<String, List<String>> map = new HashMap<String, List<String>>();
#SuppressWarnings({ "resource", "null", "unlikely-arg-type" })
public ImageLabelReader(String labelMappingFile, String imageMappingFile) throws IOException {
Map<Integer, String> map1 = new HashMap<Integer, String>();
Map<Integer, List<String>> map2 = new HashMap<Integer, List<String>>();
BufferedReader labelIn = new BufferedReader(new FileReader(labelMappingFile));
BufferedReader imageIn = new BufferedReader(new FileReader(imageMappingFile));
String row;
String[] rowArray;
while ((row = labelIn.readLine()) != null) {
rowArray = row.split(" ", 2);
map1.put(Integer.parseInt(rowArray[0]), rowArray[1]);
}
labelIn.close();
while ((row = imageIn.readLine()) != null) {
rowArray = row.split(" ", 2);
if(map2.containsKey(Integer.parseInt(rowArray[1]))) {
List<String> tempList = map2.get(Integer.parseInt(rowArray[1]));
tempList.add(rowArray[0]);
} else {
List<String> l = new ArrayList<String>();
l.add(rowArray[0]);
map2.put(Integer.parseInt(rowArray[1]), l);
}
}
imageIn.close();
List<String> t = new ArrayList<String>();
for(int i = 0; i < map1.size(); i++) {
t.clear();
for(String s : map2.get(i)) {
t.add(s);
System.out.println(t);
}
map.put(map1.get(i), map2.get(i));
}
System.out.println(map.containsKey("burrito"));
System.out.print(map2.get("burrito"));
}
Output is "True null" when the output should be "True [list containing strings]"
Try replacing -
map.put(map1.get(i), map2.get(i));
with
map.put(map1.get(i), t);
And also -
System.out.print(map2.get("burrito"));
with
System.out.print(map.get("burrito"));
Also, you're trying to get map's value using a String while you said the key is of int type, please check that.
I want to print a array list, in that array list it contains hash map and I print in a text file. while trying to print the text file it print in single line. I need in a separate line
Example:
ArrayList<Object> mainlist= new ArrayList<>();
LinkedHashMap<String, String> hmap = new LinkedHashMap<>();
for (int i=0;i<5;i++)
{
hmap.put("key1", "03-08-2018");
hmap.put("key2", "xyz";
hmap.put("key3", "123");
//ArrayList USed:::
mainlist.add(hmap);
mainlist.add("\n");
}
return mainlist;
I return in text file. It generates a single line but I need separate lines in my output text file.
Expected output in text file:
[{key1=03-08-2018,key2=xyz,key3=123}
{key1=03-08-2018,key2=xyz,key3=123}
{key1=03-08-2018,key2=xyz,key3=123}
]
Actual output in text file:
[{key1=03-08-2018,key2=xyz,key3=123},{key1=03-08-2018,key2=xyz,key3=123},{key1=03-08-2018,key2=xyz,key3=123}]
Can any one help me to out of this?
Thanks for ur reply
I tested your code and it's working for me. How Are you writing it to file?
I did it like this:
Path path = Paths.get("/test/outputXXXX.txt");
ArrayList<Object> mainlist= new ArrayList<>();
LinkedHashMap<String, String> hmap = new LinkedHashMap<>();
for (int i=0;i<5;i++)
{
hmap.put("key1", "03-08-2018");
hmap.put("key2", "xyz");
hmap.put("key3", "123");
//ArrayList USed:::
mainlist.add(hmap);
mainlist.add("\n");
}
try (BufferedWriter writer = Files.newBufferedWriter(path))
{
writer.write(mainlist.toString());
}
And output in file:
[{key1=03-08-2018, key2=xyz, key3=123},
, {key1=03-08-2018, key2=xyz, key3=123},
, {key1=03-08-2018, key2=xyz, key3=123},
, {key1=03-08-2018, key2=xyz, key3=123},
, {key1=03-08-2018, key2=xyz, key3=123},
]
EDIT:
Sorry, didin't see you need it without comma.
You can do this like that then:
Path path = Paths.get("/test/outputXXXX.txt");
ArrayList<Object> mainlist= new ArrayList<>();
LinkedHashMap<String, String> hmap = new LinkedHashMap<>();
for (int i=0;i<5;i++)
{
hmap.put("key1", "03-08-2018");
hmap.put("key2", "xyz");
hmap.put("key3", "123");
//ArrayList USed:::
mainlist.add(hmap);
mainlist.add("\n");
}
try (BufferedWriter writer = Files.newBufferedWriter(path))
{
writer.write("[");
for (Object o : mainlist) {
writer.write(o.toString());
}
writer.write("]");
}
ArrayList<Object> mainlist= new ArrayList<>();
LinkedHashMap<String, String> hmap = new LinkedHashMap<>();
for (int i=0;i<5;i++)
{
hmap.put("key1", "03-08-2018");
hmap.put("key2", "xyz"); //you missed closing paranthesis here
hmap.put("key3", "123");
//ArrayList USed:::
mainlist.add(hmap);
mainlist.add("\n");
}
return mainlist;
You can try the below code in :: https://www.tutorialspoint.com/compile_java_online.php
import java.util.*;
public class ArrayListExample{
public static void main(String args[]){
ArrayList<Object> mainlist= new ArrayList<>();
LinkedHashMap<String, String> hmap = new LinkedHashMap<>();
int i=0;
for (i=0;i<5;i++) {
hmap.put("key1", "03-08-2018");
hmap.put("key2", "xyz");
hmap.put("key3", "123");
//ArrayList USed:::
mainlist.add(hmap);
mainlist.add("\n");
}
System.out.println(mainlist);
return;
}
}
This gives your expected output. Hope this helps you.
Thanks.
I want to retrieve the value of key in a Hashmap that is in another Hashmap,
static HashMap<String , HashMap<String, Float>> terms = new HashMap();
static String date;
public static void main(String[] args) throws FileNotFoundException, ParseException, IOException {
InputStream ips=new FileInputStream(filePath);
InputStreamReader ipsr=new InputStreamReader(ips);
BufferedReader br=new BufferedReader(ipsr);
String ligne;
while ((ligne=br.readLine())!=null){
JSONParser jsonParser = new JSONParser();
JSONObject jsonObject = (JSONObject) jsonParser.parse(ligne);
date = (String) jsonObject.get("created_at");
String text = (String) jsonObject.get("text");
Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_36);
List<String> ss=TokenizewithAnalyzer.tokenizeString(analyzer, text);
for(String s : ss){
ajoutFrequence(s, date);}
System.out.print("==>"+ss+" \n");}
for(Entry <String, HashMap<String, Float>> entry : terms.entrySet()){
// float res=entry.getValue().get(date).floatValue();
System.out.println(entry.getValue().get(date).floatValue());
}
br.close();
}
static void ajoutFrequence(String token, String date){
if(terms.containsKey(token)){
HashMap<String, Float> freqdate = terms.get(token);
if(freqdate.containsKey(date)){
freqdate.put( date, freqdate.get(date)+1);
}else{
freqdate.put(date, Float.valueOf(1));
}
}else{
HashMap<String, Float> freqdate = new HashMap<>();
freqdate.put(date, Float.valueOf(1));
terms.put(token, freqdate);
} }}
in the output I get the frequence in a list for example:
null
null
1.0
null
null
null
I want to do something like this: float freq=entry.getValue().values(); but it is impossible.Thank you in advance.
You use the date as a key in your second map. So I assume you could do following:
for(Entry <String, HashMap<String, Float>> entry : terms.entrySet()){
System.out.println(entry.getValue().get(date));
}
To access a specific value in your second map, you need to provide a key for this value. In your case, this key is a date.
I solved the problem in fact I used two loop to traverse the hashmap and I recovered the value of the second hashmap like this:
for(Entry <String, HashMap<String, Float>> entry : terms.entrySet()){
HashMap<String, Float> d=entry.getValue();
for(Entry<String,Float>ent:d.entrySet()){
float dd=ent.getValue();
System.out.println(dd);}}
At the end I got the float. Thank you.
I have a hashmap with a String key and String value. It contains a large number of keys and their respective values.
For example:
key | value
abc | aabbcc
def | ddeeff
I would like to write this hashmap to a csv file such that my csv file contains rows as below:
abc,aabbcc
def,ddeeff
I tried the following example here using the supercsv library: http://javafascination.blogspot.com/2009/07/csv-write-using-java.html. However, in this example, you have to create a hashmap for each row that you want to add to your csv file. I have a large number of key value pairs which means that several hashmaps, with each containing data for one row need to be created. I would like to know if there is a more optimized approach that can be used for this use case.
Using the Jackson API, Map or List of Map could be written in CSV file. See complete example here
/**
* #param listOfMap
* #param writer
* #throws IOException
*/
public static void csvWriter(List<HashMap<String, String>> listOfMap, Writer writer) throws IOException {
CsvSchema schema = null;
CsvSchema.Builder schemaBuilder = CsvSchema.builder();
if (listOfMap != null && !listOfMap.isEmpty()) {
for (String col : listOfMap.get(0).keySet()) {
schemaBuilder.addColumn(col);
}
schema = schemaBuilder.build().withLineSeparator(System.lineSeparator()).withHeader();
}
CsvMapper mapper = new CsvMapper();
mapper.writer(schema).writeValues(writer).writeAll(listOfMap);
writer.flush();
}
Something like this should do the trick:
String eol = System.getProperty("line.separator");
try (Writer writer = new FileWriter("somefile.csv")) {
for (Map.Entry<String, String> entry : myHashMap.entrySet()) {
writer.append(entry.getKey())
.append(',')
.append(entry.getValue())
.append(eol);
}
} catch (IOException ex) {
ex.printStackTrace(System.err);
}
As your question is asking how to do this using Super CSV, I thought I'd chime in (as a maintainer of the project).
I initially thought you could just iterate over the map's entry set using CsvBeanWriter and a name mapping array of "key", "value", but this doesn't work because HashMap's internal implementation doesn't allow reflection to get the key/value.
So your only option is to use CsvListWriter as follows. At least this way you don't have to worry about escaping CSV (every other example here just joins with commas...aaarrggh!):
#Test
public void writeHashMapToCsv() throws Exception {
Map<String, String> map = new HashMap<>();
map.put("abc", "aabbcc");
map.put("def", "ddeeff");
StringWriter output = new StringWriter();
try (ICsvListWriter listWriter = new CsvListWriter(output,
CsvPreference.STANDARD_PREFERENCE)){
for (Map.Entry<String, String> entry : map.entrySet()){
listWriter.write(entry.getKey(), entry.getValue());
}
}
System.out.println(output);
}
Output:
abc,aabbcc
def,ddeeff
Map<String, String> csvMap = new TreeMap<>();
csvMap.put("Hotel Name", hotelDetails.getHotelName());
csvMap.put("Hotel Classification", hotelDetails.getClassOfHotel());
csvMap.put("Number of Rooms", hotelDetails.getNumberOfRooms());
csvMap.put("Hotel Address", hotelDetails.getAddress());
// specified by filepath
File file = new File(fileLocation + hotelDetails.getHotelName() + ".csv");
// create FileWriter object with file as parameter
FileWriter outputfile = new FileWriter(file);
String[] header = csvMap.keySet().toArray(new String[csvMap.size()]);
String[] dataSet = csvMap.values().toArray(new String[csvMap.size()]);
// create CSVWriter object filewriter object as parameter
CSVWriter writer = new CSVWriter(outputfile);
// adding data to csv
writer.writeNext(header);
writer.writeNext(dataSet);
// closing writer connection
writer.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
If you have a single hashmap it is just a few lines of code. Something like this:
Map<String,String> myMap = new HashMap<>();
myMap.put("foo", "bar");
myMap.put("baz", "foobar");
StringBuilder builder = new StringBuilder();
for (Map.Entry<String, String> kvp : myMap.entrySet()) {
builder.append(kvp.getKey());
builder.append(",");
builder.append(kvp.getValue());
builder.append("\r\n");
}
String content = builder.toString().trim();
System.out.println(content);
//use your prefered method to write content to a file - for example Apache FileUtils.writeStringToFile(...) instead of syso.
result would be
foo,bar
baz,foobar
My Java is a little limited but couldn't you just loop over the HashMap and add each entry to a string?
// m = your HashMap
StringBuilder builder = new StringBuilder();
for(Entry<String, String> e : m.entrySet())
{
String key = e.getKey();
String value = e.getValue();
builder.append(key);
builder.append(',');
builder.append(value);
builder.append(System.getProperty("line.separator"));
}
string result = builder.toString();