How can I sort JSON by ID?

Processing Coding Questions
21

How can I evaluate whether a String is numeric? (Contains only numbers?)

like s1.isNumeric() of type boolean

22

There are lots of ways of doing this in Java. The best solutions depend on the specific use case. Do you need to support negative numbers? Can they be a decimal, and is it localized (. vs , etc)? Will there be scientific notation?

23

You could submit a proposed change – processing/core/src/processing/data/JSONArray.java at master · processing/processing · GitHub

Or if you don’t want a wrapper function, you can extend JSONArray yourself. Here is an example based on the JSONArray reference example, but using a simple JSONObject id String comparator as in our discussion.

/**
 * JSONArraySorting
 * 2019-12 Extend JSONArray and add a custom sort
 */

// begin with the reference JSONArray example:
// https://processing.org/reference/JSONArray.html

import java.util.Collections;  // added
import java.util.Comparator;   // added 

String[] species = { "Capra hircus", "Panthera pardus", "Equus zebra" };
String[] names = { "Goat", "Leopard", "Zebra" };
JSONArraySortable values;            // change to extended class

void setup() {
  values = new JSONArraySortable();  // change to extended class
  for (int i = 0; i < species.length; i++) {
    JSONObject animal = new JSONObject();
    animal.setString("id", ""+(species.length-i));  // number w/Strings, 3-2-1
    animal.setString("species", species[i]);
    animal.setString("name", names[i]);
    values.setJSONObject(i, animal);
  }
  saveJSONArray(values, "data/new.json");   // saves 3-2-1
 
  // now sort the array by its object "id" keys and save it again
  values.sort();
  saveJSONArray(values, "data/new2.json");  // saves 1-2-3
  
}

class JSONArraySortable extends JSONArray {
  
  // pairwise comparison logic for sort is in the Comparator
  class JSONComparator implements Comparator<JSONObject> {
    @Override
      public int compare (JSONObject a, JSONObject b) {
      return Long.compare(Long.valueOf(a.getString("id")), Long.valueOf(b.getString("id")));
    }
  }
  
  // utility -- sort will need to get all objects from private ArrayList
  ArrayList<JSONObject> getAll() {
    ArrayList<JSONObject> myobjs = new ArrayList<JSONObject>();
    for (int i=0; i<this.size(); i++) {
      myobjs.add((JSONObject)this.get(i));
    }
    return myobjs;
  }
  
  // utility -- sort will need to clear all objects from private ArrayList
  public void clear() {
    for (int i=this.size()-1; i>=0; i--) {
      this.remove(i);
    }
  }
  
  // sort by getting all objects, sorting with comparator, clearing, and appending
  public void sort() {
    ArrayList<JSONObject> myobjs = this.getAll();
    Collections.sort(myobjs, new JSONComparator());
    this.clear();
    for (int i=0; i<myobjs.size(); i++) {
      this.append(myobjs.get(i));
    }
  }
}
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