To extract scalar values from a JSON payload, instantiate the parser with the raw response string and retrieve fields by their corresponding keys.

String payload = "{\"target\":\"https://developer.android.com\"}";
JSONObject rootObject = new JSONObject(payload);
String endpoint = rootObject.getString("target");

Complex objects containing multiple key-value pairs follow the same initialization pattern. Each field requires a separate extracsion call matching the expected type.

String deviceMetadata = "{\"model\":\"Pixel7\", \"build\":\"SAR3.220829.015\"}";
JSONObject metadataRoot = new JSONObject(deviceMetadata);
String modelType = metadataRoot.getString("model");
String firmwareVersion = metadataRoot.getString("build");
Log.d("ParseResult", String.format("Model: %s | Version: %s", modelType, firmwareVersion));

Iterating through numeric or string arrays requires fetching the collection first, then looping over its length. The getter method must correspond to the underlying data type stored at each index.

String sequenceData = "{\"indices\":[10, 20, 30]}";
JSONObject sequenceObj = new JSONObject(sequenceData);
JSONArray indexArray = sequenceObj.getJSONArray("indices");

for (int idx = 0; idx < indexArray.length(); idx++) {
    int currentVal = indexArray.getInt(idx);
    Log.i("Sequence", String.valueOf(currentVal));
}

Hierarchical arrays containing nested collections can be traversed by chaining array accessors within the iteration loop.

String matrixPayload = "{\"data\":[[5], [10], [15]]}";
JSONObject matrixRoot = new JSONObject(matrixPayload);
JSONArray outerCollection = matrixRoot.getJSONArray("data");

for (int i = 0; i < outerCollection.length(); i++) {
    JSONArray innerPair = outerCollection.getJSONArray(i);
    System.out.println(innerPair.getInt(0));
}

When a JSON node contains an array of sub-objects, switch the iteration logic to retrieve JSONObject instances instead of primitive values.

String catalogResponse = "{\"devices\":[{\"type\":\"smartphone\"}, {\"type\":\"tablet\"]}";
JSONObject catalogRoot = new JSONObject(catalogResponse);
JSONArray productItems = catalogRoot.getJSONArray("devices");

for (int n = 0; n < productItems.length(); n++) {
    JSONObject itemInfo = productItems.getJSONObject(n);
    System.out.println(itemInfo.getString("type"));
}

Direct accessor methods like getString() or getInt() will throw a JSONException if the specified key is absent. For production environments, utilize the opt variant which returns safe defaults or null upon failure, preventing unexpected crashes during network responses.

// Triggers JSONException if 'status' does not exist
String statusDirect = responseJson.getString("status");

// Returns null gracefully when 'status' is missing
String statusSafe = responseJson.optString("status");

// Returns fallback value 0 if 'count' key is undefined
int countDefault = responseJson.optInt("count", 0);

Files saved with UTF-8 encoding on Windows systems may include a Byte Order Mark (BOM), represented as a hidden  character at the beginning of the stream. This invisible prefix causes standard JSON parsers to fail immediately. Strip the malformed characters dynamically before instantiation.

String rawInput = loadFileContent("data.json");

// Locate opening brace and truncate preceding BOM bytes
int startMarker = rawInput.indexOf('{');
int endMarker = rawInput.lastIndexOf('}') + 1;

if (startMarker > 0 && endMarker > startMarker) {
    rawInput = rawInput.substring(startMarker, endMarker);
}

JSONObject cleanParsed = new JSONObject(rawInput);