Java : Replacing Last character of a String and First character of the String

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 .

I would use a proper JSON deserializer and serializer like json.org/java. — Vikdor
– Vikdor, Commented Nov 5, 2012 at 4:38

DaoWen · Accepted Answer · 2012-11-05 04:43:17Z

5

{ 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);

edited Nov 5, 2012 at 4:43

answered Nov 5, 2012 at 4:32

DaoWen

33.1k6 gold badges77 silver badges102 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Bhesh Gurung · Accepted Answer · 2012-11-05 04:43:06Z

1

Of course, regex doesn't look like a very good tool for this. But the following seem to work:

String str = "{..{...}..}}";
str = str.replaceFirst("\\{", "");
str = str.replaceFirst("}$", ","); 
System.out.println(str);

Output:

..{...}..},

answered Nov 5, 2012 at 4:43

Bhesh Gurung

51.1k23 gold badges96 silver badges147 bronze badges

3 Comments

DaoWen Over a year ago

I think str.replaceFirst("}$", ","); works just fine for the 2nd replace, and it has 4 fewer backslashes.

Bhesh Gurung Over a year ago

@DaoWen: Thanks. Added it to the answer, and that sure does look better. :)

DaoWen Over a year ago

Java really needs some sort of raw string syntax you can use for regular expressions like they have in Scala and C#. I wrote a regex a little while back that needed five backslashes in a row to get the escaping right in Java. Bleh.

Yogendra Singh · Accepted Answer · 2012-11-05 04:46:33Z

0

Some issues in your first two statements. Add 0 as start index in substring method and leave with that. Put \\ as escape char in matching pattern and ut a , in second statement as replacement value.

String  Astr = A.substring(0, A.length()-1);//truncate the ending `}`
String  Bstr = B.replaceFirst("\\{", ",");//replaces first '{` with a ','
String totalString =  Astr + Bstr ;

Please note: There are better ways, but I am just trying to correct your statements.

edited Nov 5, 2012 at 4:46

answered Nov 5, 2012 at 4:40

Yogendra Singh

34.5k7 gold badges66 silver badges73 bronze badges

Collectives™ on Stack Overflow

Java : Replacing Last character of a String and First character of the String

3 Answers 3

Comments

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related