Java Program To Convert String To HashMap

Example 1: Convert below String to HashMap

String str = "{name = rahul,email = rahul@knf.co.in,gender = male}";

Solution 1: Before Java 8 

 public static void main(String[] args) {

        String str = "{name = rahul,email = rahul@knf.co.in,gender = male}";
        
        //Remove curly brackets.
        str = str.substring(1, str.length() - 1); 
        //Split the string by , to get key-value pairs
        String[] keyValuePairs = str.split(","); 
        Map<String, String> map = new HashMap<>();
        //Iterate over the pairs
        for (String pair : keyValuePairs) 
        {
            //Split the pairs to get key and value 
            String[] entry = pair.split("="); 
            //Add them to the hashmap and trim whitespaces
            map.put(entry[0].trim(), entry[1].trim()); 
        }
        System.out.println(map);
    }

Solution 2: Using Java 8 Stream 

public static void main(String[] args) {
        String str = "{name = rahul,email = rahul@knf.co.in,gender = male}";
        
        Map<String, String> map = Arrays.
                    stream(str.substring(1, str.length() - 1).
                               split(","))
                                 .map(s -> s.split("=", 2))
        .collect(Collectors.toMap(s -> s[0].trim(), 
                               s -> s[1].trim()));
        System.out.println(map);
    }

• Arrays.stream() to convert string array to stream. 

• str.substring(1, str.length() - 1) removes curly brackets. 

• split(","): Split the string to get individual map entries. 

• s.split("=", 2): Split them by = to get the key and the value and ensure that the array is never larger than two elements. 

• The collect() method in Stream API collects all objects from a stream object and stores them in the type of collection. 

• Collectors.toMap(s -> s[0].trim(), s -> s[1].trim()): Accumulates elements into a Map whose keys and values are the result of applying the provided mapping functions to the input elements. 

Example 2: Convert  below String to HashMap 

String str = "[name = rahul:email = rahul@knf.co.in:gender = male]";

Solution 1: Before Java 8 

  public static void main(String[] args) {

        String str = "[name = rahul:email = rahul@knf.co.in:gender = male]";
        
        //Remove square brackets
        str = str.substring(1, str.length() - 1); 

        //Split the string by : to get key-value pairs
        String[] keyValuePairs = str.split(":"); 

        Map<String, String> map = new HashMap<>();

        //Iterate over the pairs
        for (String pair : keyValuePairs) 
        {
            //Split the pairs to get key and value 
            String[] entry = pair.split("="); 

            //Add them to the hashmap and trim whitespaces
            map.put(entry[0].trim(), entry[1].trim()); 
        }
        System.out.println(map);
    }

Solution 2: Using Java 8 Stream 

public static void main(String[] args) {

        String str = "[name = rahul:email = rahul@knf.co.in:gender = male]";
        
        Map<String, String> map = Arrays.
                    stream(str.substring(1, str.length() - 1).
                               split(":"))
                                 .map(s -> s.split("=", 2))
        .collect(Collectors.toMap(s -> s[0].trim(), 
                               s -> s[1].trim()));
        System.out.println(map);
    }

• Arrays.stream() to convert string array to stream. 

• str.substring(1, str.length() - 1) removes square brackets. 

• split(":"): Split the string to get individual map entries. 

• s.split("=", 2): Split them by = to get the key and the value and ensure that the array is never larger than two elements. 

• The collect() method in Stream API collects all objects from a stream object and stores them in the type of collection.

• Collectors.toMap(s -> s[0].trim(), s -> s[1].trim()): Accumulates elements into a Map whose keys and values are the result of applying the provided mapping functions to the input elements. 

More interesting topics... 

Test Slices in Spring-Boot

• Testing Spring Web Controller with @WebMvcTest

• Testing Spring WebFlux Controller with @WebFluxTest

• Testing JSON Serialization and Deserialization With @JsonTest

• Testing REST Clients With @RestClientTest

• Testing a JPA application With @DataJpaTest

• Testing JDBC components with @JdbcTest

• Testing Spring Data JDBC application with @DataJdbcTest

• Testing a MongoDB application with @DataMongoTest

• Testing a JPA application with @DataJpaTest and Testcontainers

• Testing a Data MongoDB application with Testcontainers and @DataMongoTest

Integration Testing

• Spring Boot 3 + PostgreSQL - Integration Testing with Testcontainers

• Spring Boot MongoDB - Integration Testing with Testcontainers