Question

I want to add Two java JSON String manually , so for this i need to remove “}” and replace it with comma “,” of first JSON String and remove the first “{“ of the second JSON String .
This is my program

import java.util.Map;
import org.codehaus.jackson.type.TypeReference;
public class Hi {
    private static JsonHelper jsonHelper = JsonHelper.getInstance();
    public static void main(String[] args) throws Exception {

        Map<String, Tracker> allCusts = null;

String A = "{\"user5\":{\"Iden\":4,\"Num\":1},\"user2\":{\"Iden\":5,\"Num\":1}}";

String B = "{\"user1\":{\"Iden\":4,\"Num\":1},\"user3\":{\"Iden\":6,\"Num\":1},\"user2\":{\"Iden\":5,\"Num\":1}}";

        String totalString = A + B;
        if (null != totalString) {
            allCusts = (Map<String, Tracker>) jsonHelper.toObject(
                    totalString, new TypeReference<Map<String, Tracker>>() {
                    });

        }
        System.out.println(allCusts);
    }
}

When adding two Strings A + B

I want to remove the last character of “}” in A and replace it with “,” and remove the FIrst character of “{” in B .

SO this should it look like .

String A = "{\"user5\":{\"Iden\":4,\"Num\":1},\"user2\":{\"Iden\":5,\"Num\":1},";

String B = "\"user1\":{\"Iden\":4,\"Num\":1},\"user3\":{\"Iden\":6,\"Num\":1},\"user2\":{\"Iden\":5,\"Num\":1}}";

I have tried

String  Astr = A.replace(A.substring(A.length()-1), ",");
String  Bstr = B.replaceFirst("{", "");

String totalString =  Astr + Bstr ;

With this i was getting

Exception in thread “main” java.util.regex.PatternSyntaxException: Illegal repetition

please suggest .

Answer 1

{ is a control character for Regular Expressions, and since replaceFirst takes a string representation of a Regular Expression as its first argument, you need to escape the { so it’s not treated as a control character:

String  Bstr = B.replaceFirst("\\{", "");

---

I would say that using the replace methods is really overkill here since you’re just trying to chop a character off of either end of a string. This should work just as well:

String totalString = A.substring(0, A.length()-1) + "," + B.substring(1);