How to convert String into Hashmap in java

问题

How can I convert a String into a HashMap?

String value = "{first_name = naresh, last_name = kumar, gender = male}"

into

Map<Object, Object> = {
    first_name = naresh,
    last_name = kumar,
    gender = male
}

Where the keys are first_name, last_name and gender and the values are naresh, kumar, male.

Note: Keys can be any thing like city = hyderabad.

I am looking for a generic approach.

回答1:

This is one solution. If you want to make it more generic, you can us StringUtils library.

String value = "{first_name = naresh,last_name = kumar,gender = male}";
value = value.substring(1, value.length()-1);           //remove curly brackets
String[] keyValuePairs = value.split(",");              //split the string to creat key-value pairs
Map<String,String> map = new HashMap<>();               

for(String pair : keyValuePairs)                        //iterate over the pairs
{
    String[] entry = pair.split("=");                   //split the pairs to get key and value 
    map.put(entry[0].trim(), entry[1].trim());          //add them to the hashmap and trim whitespaces
}

For example you can switch

 value = value.substring(1, value.length()-1);

to

 value = StringUtils.substringBetween(value, "{", "}");

if you are using StringUtils which is contained in apache.commons.lang package.

回答2:

String value = "{first_name = naresh,last_name = kumar,gender = male}"

Let's start

1. Remove { and } from the String>>first_name = naresh,last_name = kumar,gender = male
2. Split the String from ,>> array of 3 element
3. Now you have an array with 3 element
4. Iterate the array and split each element by =
5. Create a Map<String,String> put each part separated by =. first part as Key and second part as Value

回答3:

Since I use Gson quite liberally, I can share a Gson based approach:

Map<Object,Object> attributes = gson.fromJson(gson.toJson(value)),Map.class);

What it does is:

1. gson.toJson(value) will serialize your object into its equivalent Json representation.
2. gson.fromJson will convert the Json string to specified object. (in this example - Map)

The flexibility with this approach is that you can pass an Object instead of String to toJson method.

回答4:

@Test
public void testToStringToMap() {
    Map<String,String> expected = new HashMap<>();
    expected.put("first_name", "naresh");
    expected.put("last_name", "kumar");
    expected.put("gender", "male");
    String mapString = expected.toString();
    Map<String, String> actual = Arrays.stream(mapString.replace("{", "").replace("}", "").split(","))
            .map(arrayData-> arrayData.split("="))
            .collect(Collectors.toMap(d-> ((String)d[0]).trim(), d-> (String)d[1]));

    expected.entrySet().stream().forEach(e->assertTrue(actual.get(e.getKey()).equals(e.getValue())));
}

回答5:

try this out :)

public static HashMap HashMapFrom(String s){
    HashMap base = new HashMap(); //result
    int dismiss = 0; //dismiss tracker
    StringBuilder tmpVal = new StringBuilder(); //each val holder
    StringBuilder tmpKey = new StringBuilder(); //each key holder

    for (String next:s.split("")){ //each of vale
        if(dismiss==0){ //if not writing value
            if (next.equals("=")) //start writing value
                dismiss=1; //update tracker
            else
                tmpKey.append(next); //writing key
        } else {
            if (next.equals("{")) //if it's value so need to dismiss
                dismiss++;
            else if (next.equals("}")) //value closed so need to focus
                dismiss--;
            else if (next.equals(",") //declaration ends
                    && dismiss==1) {
                //by the way you have to create something to correct the type
                Object ObjVal = object.valueOf(tmpVal.toString()); //correct the type of object
                base.put(tmpKey.toString(),ObjVal);//declaring
                tmpKey = new StringBuilder();
                tmpVal = new StringBuilder();
                dismiss--;
                continue; //next :)
            }
            tmpVal.append(next); //writing value
        }
    }
    Object objVal = object.valueOf(tmpVal.toString()); //same as here
    base.put(tmpKey.toString(), objVal); //leftovers
    return base;
}

examples input : "a=0,b={a=1},c={ew={qw=2}},0=a" output : {0=a,a=0,b={a=1},c={ew={qw=2}}}

来源：https://stackoverflow.com/questions/26485964/how-to-convert-string-into-hashmap-in-java