How can I get a special part in a string in Java?

Question

I have to read commands from a file I have and take necessary actions according to each command. I was able to find out the process of reading from the file and what the command is, but I am having trouble transferring the specific information contained in the command to the program. As an example, the line read is as follows

Add id:12 name:"Sandik" singer:"Muslum Gurses" year:2009 count:5 price:20

I have separated this reading line in each space as u can see in below.

 Scanner scan = new Scanner(new File(args[0]));
 while (scan.hasNextLine()) {
      String data = scan.nextLine();
      String[] readedCommand = data.split(" ");

After this operation, readedCommands[0] gives me the read command. For the above example, readedCommands[0] = "Add"

After this step, I need to extract the information from the rest of the command, but I have no idea how to extract information such as id, name, singer. I will be grateful if you could help me. Thank you in advance.

Answer 1

After you have the array then you can split each string again by split(":") to separate the key from the value. Use a HashMap to store the key and values.

HashMap<String, String> hmap = new HashMap<String, String>();
 while (scan.hasNextLine()) {
      String data = scan.nextLine();
      String[] readedCommand = data.split(" ");
      for(int i = 1; i < readedCommand.length; i++){
          String[] pair = readedCommand[i].split(";");
          hmap.put(pair[0], pair[1]);
      }

}

Answer 2

You can do it by splitting the string twice:

1. Split the given string, using the regex, \s(?=\w+:)
2. Then iterate the resulting array from the index, 1 (because the string at index, 0 is the command) and split each element further on :

Demo:

public class Main {
    public static void main(String[] args) {
        String data = "Add id:15 singer:\"Tarkan\" name:\"Adimi Kalbine Yaz\" year:2010 count:10 price:20";

        // First, split on whitespace
        String[] parts = data.split("\\s(?=\\w+:)");

        // The first element in the array is the command
        String command = parts[0];
        System.out.println("Command: " + command);

        // Split the remaining elements on ':'
        for (int i = 1; i < parts.length; i++) {
            String[] keyVal = parts[i].split(":");
            if (keyVal.length == 2) {
                String key = keyVal[0];
                String value = keyVal[1];
                System.out.println("Key: " + key + ", Value: " + value);
            }
        }
    }
}

Output:

Command: Add
Key: id, Value: 15
Key: singer, Value: "Tarkan"
Key: name, Value: "Adimi Kalbine Yaz"
Key: year, Value: 2010
Key: count, Value: 10
Key: price, Value: 20

Explanation of the regex, \s(?=\w+:):

1. \s specifies whitespace.
2. (?=\w+:) specifies positive lookahead for one or more word character(s) followed by a :

Answer 3

Consider the following code. Comments in the code serve as explanation of what it does.

// Text block, first introduced as preview feature in JDK 13
String str = """
        Add id:12 name:"Sandik" singer:"Muslum Gurses" year:2009 count:5 price:20\
        """;
String[] parts = str.split(" ", 2);  // Create an array with no more than two elements.
System.out.println(Arrays.toString(parts));

// A single space that is not preceded by a quote mark followed by one or more word characters
// and also not succeeded by a string of one or more word characters followed by a quote.
String regex = "(?<!\"\\w+)\\s(?!\\w+\")";

// Splits on every space except for the space between 'Muslum' and 'Gurses'.
String[] list = parts[1].split(regex);
System.out.println(Arrays.toString(list));

// Used in the stream operation below.
// Split the string (elem) at the colon character and return the first array element.
Function<String, String> keyMapper = elem -> elem.split(":")[0];

// Used in the stream operation below.
Function<String, String> valueMapper = elem -> elem.split(":")[1];

Map<String, String> map = Arrays.stream(list)
                                .collect(Collectors.toMap(keyMapper, valueMapper));
System.out.println(map);

Running above code produces the following output.

[Add, id:12 name:"Sandik" singer:"Muslum Gurses" year:2009 count:5 price:20]
[id:12, name:"Sandik", singer:"Muslum Gurses", year:2009, count:5, price:20]
{singer="Muslum Gurses", year=2009, price=20, name="Sandik", count=5, id=12}