How to Access and Extract Values from a Nested JSONArray in Java?

Accessing Member Values from a JSONArray in Java

Navigating through a JSONArray can be a challenge for those new to JSON parsing. Let's consider a scenario where you need to retrieve specific values from a nested JSON structure.

Suppose you have a JSON file with the following structure:

{
  "locations": {
    "record": [
      {
        "id": 8817,
        "loc": "NEW YORK CITY"
      },
      {
        "id": 2873,
        "loc": "UNITED STATES"
      },
      {
        "id": 1501,
        "loc": "NEW YORK STATE"
      }
    ]
  }
}

Using Java's JSON parsing capabilities, you can access the "record" JSONArray using the following code:

JSONObject req = new JSONObject(join(loadStrings(data.json),""));
JSONObject locs = req.getJSONObject("locations");
JSONArray recs = locs.getJSONArray("record");

To iterate through the "record" JSONArray and extract the "id" and "loc" values, you can employ the following loop:

for (int i = 0; i < recs.length(); ++i) {
    JSONObject rec = recs.getJSONObject(i);
    int id = rec.getInt("id");
    String loc = rec.getString("loc");
    // ...
}

Here's how each line of code contributes to the solution:

• recs.length(): Obtains the length of the JSONArray, indicating the number of records it contains.
• recs.getJSONObject(i): Retrieves the ith JSONObject within the JSONArray.
• rec.getInt("id") and rec.getString("loc"): Extracts the "id" (an integer) and "loc" (a string) values from the JSONObject.
• The ... represents the subsequent operations you can perform with the extracted values.

By combining these techniques, you'll be able to efficiently access and utilize the data within a JSONArray in your Java application.

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