[
    {
        "vendor_itms_arr": [
            "265",
            "141",
            "148"
        ]
    }
]

import java.util.ArrayList;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;


public class MrTest {

    public static void main(String args[]) throws JSONException
    {
        String json = "[rn" +
                "    {rn" +
                "        "vendor_itms_arr": [rn" +
                "            "265",rn" +
                "            "141",rn" +
                "            "148"rn" +
                "        ]rn" +
                "    }rn" +
                "]";

        JSONArray array = new JSONArray(json);
        ArrayList<Integer> vendor_itms_arr = new ArrayList<Integer>();
        for(int i=0;i<array.length();i++)
        {
             JSONObject jb1 = array.getJSONObject(i);
             JSONArray jr1 = jb1.getJSONArray("vendor_itms_arr");
            if (jr1 != null) {
                   int len = jr1.length();
                   for (int k=0;i<len;i++){
                       int val = (Integer) jr1.get(k);
                       vendor_itms_arr.add(val);
                   }
                }
        }
        System.out.println(vendor_itms_arr);
    }
}

Exception in thread "main" java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
    at MrTest.main(MrTest.java:36)

int constructed_array[] = { 265 , 141 , 148};