Java string find and replace with different value each time for a key

Question

I am facing trouble to replace some value inside a string.

{"key1":"value1","key2":"value2","key3":"value3","key4":"djdhsja","BizProcessNm":"value5",.........}

I have to replace the value of key4 to "something". As shown below

{"key1":"value1","key2":"value2","key3":"value3","key4":"something","BizProcessNm":"value5",.........}

The problem is I don't know the exact value inside the value of key4. In this case, "djdhsja" is the value. It will be random.

I thought of getting the position of key4 in the string and then based on the string position, replace the content after first " till it ends with "something". But this may be a little complicated as i have to do this for so many strings inside a for loop(The loop was written by someone else, I am just modifying it).

Is there any regex kind of find and replace like sed in linux.

edit: The position of key4 is random

why don't use JSON parser?

Youcef LAIDANI
– Youcef LAIDANI

2017-06-19 09:26:15 +00:00
Commented Jun 19, 2017 at 9:26 — Youcef LAIDANI
– Youcef LAIDANI, Commented Jun 19, 2017 at 9:26

Markus Benko · Accepted Answer · 2017-06-19 09:37:11Z

1

Assuming that there is no whitespace between key, colon and value and also no quotation mark inside the current value of key4 you can use the following line of code to replace the value:

s.replaceFirst("(?<=\\\"key4\\\":\\\")(.*?)(?=\\\")", "new value");

The regex is using positive look-behind and look-ahead so that only the text inside the quotation marks of the value is replaced.

While this may be applicable for a one-time action I'd rather suggest using a JSON-parser as suggested in the comments and Marcell's answer.

answered Jun 19, 2017 at 9:37

Markus Benko

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2 Comments

DileepGogula Over a year ago

I am actually looking for a solution like this. Thanks for the help. Actually, i have to iterate over some 1000's of records which they are iterating over a loop, creating a JSON object and then modifying it may lead to more time complexity for each record. Your solution fulfilled the need

user1456110 Over a year ago

Hi, how do i update existing value. for ex., append some string to existing string?

Marcell · Accepted Answer · 2017-06-19 09:33:13Z

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If I'm not mistaken, you have JSON-like key-value pairs. In that case I would convert the json into a java object. There are some libraries written for that (ex. https://github.com/FasterXML/jackson). Than you can simply get and set the fields of that object.

If it is a map, or something similar, you can still get the value of "key4" by the key "key4".

And finally, if you have something totally else, like a string with that content, you can use something like:

yourString.split(",")[3].split(":")[1];

answered Jun 19, 2017 at 9:33

Marcell

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1 Comment

DileepGogula Over a year ago

I am sorry, I forgot to add that the position of key4 is random so using the array index will create a problem for me. Thanks for the help

Zia · Accepted Answer · 2017-06-19 09:59:33Z

1

You can convert your String into JSon Object and then convert that json into Map and perform your tasks,

    Map map;
    map = (Map) JSONObject.toBean(jsonObj, Map.class);
    Iterator it = map.entrySet().iterator();

Here jsonObj is json object which is get cretaed from your String value.

and on Conditional check for key, update the value of the particular key.

answered Jun 19, 2017 at 9:59

Zia

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