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java - Convert String into ArrayList<MyClass>

I want to convert a String myString like that:

[ ["cd",5,6,7], ["rtt",55,33,12], ["by65",87,87,12] ]

into an ArrayList<CustomClass>

Where CustomClass have constructor :

public CustomClass (String name, int num1, int num2, int num3)

I tried first to create ArrayList of Strings :

List<String> List = new ArrayList<String>(Arrays.asList(myString.split("[")));

Didn't worked for me...

How can I get something like that:

List - {CustomClass,CustomClass,CustomClass,CustomClass}

first CustomClass = CustomClass.name="cd" , CustomClass.num1=5,CustomClass.num2=7...

second CustomClass = CustomClass.name="rtt",CustomClass.num1=55,CustomClass.num2=55...

and so on...

See Question&Answers more detail:os

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1 Reply

0 votes
by (71.8m points)

You can do something like. If you cant guarantee the string formats then you may have to add additional checks for spliced array length and indexing.

import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

class CustomClass {
    String name;
    int num1;
    int num2;
    int num3;

    public CustomClass(String name, int num1, int num2, int num3) {
        super();
        this.name = name;
        this.num1 = num1;
        this.num2 = num2;
        this.num3 = num3;
    }
}

public class Sample {

    public static void main(String[] args) {
        String str = "[ ["cd",5,6,7], ["rtt",55,33,12], ["by65",87,87,12] ]";
        Pattern p = Pattern.compile("\[(.*?)\]");
        Matcher m = p.matcher(str.substring(1));
        List<CustomClass> customList = new ArrayList<CustomClass>();
        while (m.find()) {
            String[] arguments = m.group(1).split(",");
            customList.add(new CustomClass(arguments[0], 
                                            Integer.parseInt(arguments[1]), 
                                            Integer.parseInt(arguments[2]), 
                                            Integer.parseInt(arguments[3])));
        }
    }

}

Gson solution

public static void main(String[] args) {
    String json = "[ ["cd",5,6,7], ["rtt",55,33,12], ["by65",87,87,12] ]";
    List<CustomClass> customList = new ArrayList<CustomClass>();
    String[][] data = new Gson().fromJson(json, String[][].class);
    for (String[] strArray : data){
        customList.add(new CustomClass(strArray[0], 
                Integer.parseInt(strArray[1]), 
                Integer.parseInt(strArray[2]), 
                Integer.parseInt(strArray[3])));
    }
    System.out.println(customList);
}

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