I want hashmap to array
I create the hashmap
Map<Integer,File> selectedFiles = new Hashmap<>();
and put it some Map data
And I convert this hashmap's values to array so
File[] files = (File[]) selectedFiles.values().toArray();
But errors occur;
java.lang.Object[] cannot be cast to java.io.File[]
I know that when I want the hashmap's values to array, use .values.toArray() but maybe it is not corret;
This way is wrong?
Map<Integer, File> selectedFiles = new HashMap<>();
selectedFiles.put(1, null);
File[] files = selectedFiles.values().toArray(
new File[selectedFiles.size()]);
System.out.println(files);// We will get the object [Ljava.io.File;#15db9742
arrays. toArray without parameters creates an object array because the type information of the list is lost at runtime.
Please use below Code to convert HashMap to Array ,You can change String to File in your case.
//Creating a HashMap object
HashMap<String, String> map = new HashMap<String, String>();
//Getting Collection of values from HashMap
Collection<String> values = map.values();
//Creating an ArrayList of values
ArrayList<String> listOfValues = new ArrayList<String>(values);
// Convert ArrayList to Array
String stringArray[]=listOfValues.toArray(new String[listOfValues.size()])
I am developing the Android for Xively. I get the following text data and store into string.
{"id":111111177,"title":"G-sensor","private":"true","feed":"https://api.xively.com/v2/feeds/111111177.json","auto_feed_url":"https://api.xively.com/v2/feeds/111111177.json","status":"frozen","updated":"2014-08-05T07:14:29.783670Z","created":"2014-08-01T08:29:17.156043Z","creator":"https://xively.com/users/x22819","version":"1.0.0","datastreams":[{"id":"GPIO1","current_value":"1","at":"2014-08-05T07:14:18.991421Z","max_value":"1.0","min_value":"0.0","tags":["xyz"],"unit":{"type":"G","label":"watts"}},{"id":"GPIO2","current_value":"0","at":"2014-08-05T07:14:29.783670Z","max_value":"1.0","min_value":"0.0","tags":["xyz"],"unit":{"type":"G","label":"watts"}},{"id":"GPIO3","current_value":"1","at":"2014-08-05T06:51:08.165217Z","max_value":"1.0","min_value":"1.0"},{"id":"GPIO4","current_value":"0","at":"2014-08-05T06:51:13.029452Z","max_value":"0.0","min_value":"0.0"},{"id":"GPIO5","current_value":"1","at":"2014-08-05T06:51:20.679123Z","max_value":"1.0","min_value":"1.0"},{"id":"GPIO6","current_value":"0","at":"2014-08-05T06:51:27.057369Z","max_value":"0.0","min_value":"0.0"}],"location":{"domain":"physical"},"product_id":"w8tuBsYf835kYTjDFz9w","device_serial":"DWJAXD6N7VDZ"}
There has id and the current_value in the above data , and I want to get the data of id and the current_value from the above text like following text.
GPIO1 1
GPIO2 0
GPIO3 1
GPIO4 0
GPIO5 1
GPIO6 0
How do I capture the the data of id and the current_value from the above text ?
Can somebody teach me how to do ?
Thank in advance.
Try this:
String resultJSON = "datastreams":[{"id":"GPIO1","current_value":"1","at":"2014-08-05T07:14:18.991421Z","max_value":"1.0","min_value":"0.0","tags":["xyz"],"unit":{"type":"G","label":"watts"}},
{"id":"GPIO2","current_value":"0","at":"2014-08-05T07:14:29.783670Z","max_value":"1.0","min_value":"0.0","tags":["xyz"],"unit":{"type":"G","label":"watts"}},
{"id":"GPIO3","current_value":"1","at":"2014-08-05T06:51:08.165217Z","max_value":"1.0","min_value":"1.0"},
{"id":"GPIO4","current_value":"0","at":"2014-08-05T06:51:13.029452Z","max_value":"0.0","min_value":"0.0"},
{"id":"GPIO5","current_value":"1","at":"2014-08-05T06:51:20.679123Z","max_value":"1.0","min_value":"1.0"},
{"id":"GPIO6","current_value":"0","at":"2014-08-05T06:51:27.057369Z","max_value":"0.0","min_value":"0.0"}],"location":{"domain":"physical"},"product_id":"w8tuBsYf835kYTjDFz9w","device_serial":"DWJAXD6N7VDZ"};
JSONObject jsonRoot = new JSONObject(resultJSON);
JSONArray jsonData = jsonRoot.getJSONArray("Data");
for(int i=0; i<jsonData.lenght;i++) {
JSONObject jsonOBject = jsonData.getJSONObject(i);
Log.d(TAG, "json ("+i+") = "+jsonOBject.toString());
// do what you want with your JSONObject , i.e :add it to an ArrayList of paresed result
String ID = jsonOBject.getString("id");
}
Hope this may help you
dataList = new ArrayList<HashMap<String, String>>();
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node
myarray = jsonObj.getJSONArray("datastreams");
// looping through All myarray
for (int i = 0; i < myarray.length(); i++) {
JSONObject c = myarray.getJSONObject(i);
String id = c.getString("id");
String date = c.getString("at");
// tmp hashmap for single data
HashMap<String, String> data = new HashMap<String, String>();
// adding each child node to HashMap key => value
data.put(TAG_ID, id);
data.put(TAG_DATE, date);
// adding data to data list
dataList.add(data);
}
The data you have is actually a JSON so you can simply parse it to java POJO. I would suggest to use one of 2 most popular open source parsers GSON or Jackson.
What you have to do is:
Create java POJOs for chosen parser. To make it easier use this online tool http://www.jsonschema2pojo.org/
Copy generated java classes to your project.
Use JSON parser e.g. GSON
Let's say you named your main class as Example, with GSON you can parse it like this:
Gson gson = new Gson();
String data = ....//your JSON data
Example example = gson.fromJson(data, Example.class);
Data you would like to get will have own Java representation and will be available through getter method, e.g.:
List<Datastream> datastreams = example.getDatastreamList();
for (DataStream data : datastreams) {
String id = data.getId();
String currentValue = data.getCurrentValue();
}
Then you can do whatever you like. Please know that GSON can also read streams, so if you already parse stream to string you can skip it and pass that stream to Gson object directly.
If you don't want redundant POJOs or their parameters, you can remove them. GSON will handle it and simply ignore these values. Just make sure that data you are interested in keep the generated structure.
That's how I would do it.
I want to iterate a JSONObject by using the method keys(). The problem is that one of the key is an Integer.
Iterator it = json.getJSONObject("body").keys();
The keys() method only creates an iterator from String values and I get an exception when one of the keys is an Integer. What can I do to solve this?
please read following example
String s = "{menu:{\"1\":\"sql\", \"2\":\"android\", \"3\":\"mvc\"}}";
JSONObject jObject = new JSONObject(s);
JSONObject menu = jObject.getJSONObject("menu");
Map<String,String> map = new HashMap<String,String>();
Iterator iter = menu.keys();
while(iter.hasNext()){
String key = (String)iter.next();
String value = menu.getString(key);
map.put(key,value);
}
JSON object members are key-value pairs where the key is always a string (ref). If it's a number literal, then the JSON is invalid. You should fix whatever is producing that invalid JSON.
I've created a JSON encode where you enter a HashTable (public Hashtable<?, ?> JSonDecode(String data) {... return objJS.toString(); } ) and get a string in JSON format. That is:
If I have a Hashtable with this (Hashtable in Hashtable):
Example Hashtable:
Hashtable<String, Object> exampleHT = new Hashtable<String, Object>();
exampleHT.put("Color", "Red");
exampleHT.put("OtherKey", "OtherValue");
exampleHT.put("OtherKey2", "OtherValue2");
Hashtable<String, Object> country = new Hashtable<String, Object>();
country.put("Spain", "Madrid");
country.put("France","Paris");
country.put("Italy", "Rome");
Hashtable<String, String> pokemon = new Hashtable<String, String>();
pokemon.put("Pikachu", "Electric");
pokemon.put("Charmander","Fire");
country.put("Pokemons", pokemon);
exampleHT.put("Countries", country);
I use my function(JSonEncode(exampleHT);) and I get this string:
{
"Color":"Red",
"Countries":{
"Spain":"Madrid",
"France":"Paris",
"Italy":"Rome",
"Pokemons":{
"Pikachu":"Electric",
"Charmander":"Fire"
}
},
"OtherKey":"OtherValue",
"OtherKey2":"OtherValue2"
}
It works perfectly! My problem is to create the reverse process, with JSonDecode.
Hashtable<?, ?> hashUnknown = JSonDecode(jsonStringExample);
public Hashtable<?, ?> JSonDecode(String data) {
// I do not know how to parse json in Hashtable, without indicating the tags manually.
}
I do not know how to parse json in Hashtable, without indicating the tags manually.
That is, without it:
JSONArray menuObject = new JSONArray (jObject.getString ("Color"));
JSONArray menuObject = new JSONArray (jObject.getString ("Countries"));
This should be dynamic without knowing json content without writing manually Color, Countries, ....
Any ideas or advice? Thanks,
You can get an Iterator object (java.util.Iterator) over the keys of your JSONObject (jObject)
So you can write something like this:
Iterator<String> it = jObject.keys();
String key = null;
Object value = null;
while (it.hasNext()) {
key = it.next();
value = jObject.get(key);
// Then test the instance of the value variable
// and perform some logic
}
How can I parse json from the URL? below is my json structure which does not has tags.
[{"channelId":"0465CDBE","channelName":"ATV2"},{"channelId":"06E6923B1","channelName":"Phoenix"},{"channelId":"07B4FB7ed","channelName":"N24"},{"channelId":"115B73E39","channelName":"ORF2"},
Simply get the JSONArray
JSONArray jArr = new JSONArray(jsonString);
for(int i=0;i<jArr.length;i++)
{
String jChannel = jArr.getJSONObject(i).getString("channelId");
String jChannelName = jArr.getJSONObject(i).getString("channelName");
//you can now play with these variables or add to some list or do whatever you like.
}
The outer object is a JSONArray, so you can iterate it with a "for".
Inside your json array, you have simple json objects. You can parse it by key or iterate the keys.
You can user json object and get the value with getJSONArray
examples:
testob = {"channelId":"07B4FB7ed","channelName":"N24"}, {"channelId":"115B73E39","channelName":"ORF2"},
JSONObject jsonObject = new JSONObject(testob);
JSONArray dataArray = jsonObject.getJSONArray("data");
JSONObject jsonProductData = dataArray.getJSONObject(0);