String to HashMap JAVA

Question

I have a Java Property file and there is a KEY as ORDER. So I retrieve the VALUE of that KEY using the getProperty() method after loading the property file like below.:

String s = prop.getProperty("ORDER");

then

s ="SALES:0,SALE_PRODUCTS:1,EXPENSES:2,EXPENSES_ITEMS:3";

I need to create a HashMap from above string. SALES,SALE_PRODUCTS,EXPENSES,EXPENSES_ITEMS should be KEY of HashMap and 0,1,2,3, should be VALUEs of KEYs.

If it's hard corded, it seems like below:

Map<String, Integer> myMap  = new HashMap<String, Integer>();
myMap.put("SALES", 0);
myMap.put("SALE_PRODUCTS", 1);
myMap.put("EXPENSES", 2);
myMap.put("EXPENSES_ITEMS", 3);

Answer 1

try

 String s = "SALES:0,SALE_PRODUCTS:1,EXPENSES:2,EXPENSES_ITEMS:3";
    HashMap<String,Integer> hm =new HashMap<String,Integer>();
    for(String s1:s.split(",")){
       String[] s2 = s1.split(":");
        hm.put(s2[0], Integer.parseInt(s2[1]));
    }

Answer 2

You can also use JSONObject class from json.org to this will convert your HashMap to JSON string which is well formatted

Example:

Map<String,Object> map = new HashMap<>();
map.put("myNumber", 100);
map.put("myString", "String");

JSONObject json= new JSONObject(map);

String result= json.toString();

System.out.print(result);

result:

{'myNumber':100, 'myString':'String'}

Your can also get key from it like

System.out.print(json.get("myNumber"));

result:

100

Answer 3

Use StringTokenizer to parse the string.

String s ="SALES:0,SALE_PRODUCTS:1,EXPENSES:2,EXPENSES_ITEMS:3";
    Map<String, Integer> lMap=new HashMap<String, Integer>();


    StringTokenizer st=new StringTokenizer(s, ",");
    while(st.hasMoreTokens())
    {
        String [] array=st.nextToken().split(":");
        lMap.put(array[0], Integer.valueOf(array[1]));
    }

Answer 4

You can to use split to do it:

 String[] elements = s.split(",");
 for(String s1: elements) {
     String[] keyValue = s1.split(":");
     myMap.put(keyValue[0], keyValue[1]);
 }

Nevertheless, myself I will go for guava based solution. https://stackoverflow.com/a/10514513/1356883

Answer 5

In one line :

HashMap<String, Integer> map = (HashMap<String, Integer>) Arrays.asList(str.split(",")).stream().map(s -> s.split(":")).collect(Collectors.toMap(e -> e[0], e -> Integer.parseInt(e[1])));

Details:

1) Split entry pairs and convert string array to List<String> in order to use java.lang.Collection.Stream API from Java 1.8

Arrays.asList(str.split(","))

2) Map the resulting string list "key:value" to a string array with [0] as key and [1] as value

map(s -> s.split(":"))

3) Use collect terminal method from stream API to mutate

collect(Collector<? super String, Object, Map<Object, Object>> collector)

4) Use the Collectors.toMap() static method which take two Function to perform mutation from input type to key and value type.

toMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper)

where T is the input type, K the key type and U the value type.

5) Following lambda mutate String to String key and String to Integer value

toMap(e -> e[0], e -> Integer.parseInt(e[1]))

Enjoy the stream and lambda style with Java 8. No more loops !

Answer 6

I recommend using com.fasterxml.jackson.databind.ObjectMapper (Maven repo link: https://mvnrepository.com/artifact/com.fasterxml.jackson.core) like

final ObjectMapper mapper = new ObjectMapper();
Map<String, Object> mapFromString = new HashMap<>();
try {
    mapFromString = mapper.readValue(theStringToParse, new TypeReference<Map<String, Object>>() {
        });
} catch (IOException e) {
    LOG.error("Exception launched while trying to parse String to Map.", e);
}