Efficient parsing of first four elements of large JSON arrays - json

Question

I am using Jackson to parse JSON from a json inputStream which looks like following:
[
[ 36,
100,
"The 3n + 1 problem",
56717,
0,
1000000000,
0,
6316,
0,
0,
88834,
0,
45930,
0,
46527,
5209,
200860,
3597,
149256,
3000,
1
],
[
........
],
[
........
],
.....// and almost 5000 arrays like above
]
This is the original feed link: http://uhunt.felix-halim.net/api/p
I want to parse it and keep only the first 4 elements of every array and skip other 18 elements.
36
100
The 3n + 1 problem
56717
Code structure I have tried so far:
while (jsonParser.nextToken() != JsonToken.END_ARRAY) {
jsonParser.nextToken(); // '['
while (jsonParser.nextToken() != JsonToken.END_ARRAY) {
// I tried many approaches here but not found appropriate one
}
}
As this feed is pretty big, I need to do this efficiently with less overhead and memory.
Also there are three models to procress JSON: Streaming API, Data Binding and Tree Model. Which one is appropriate for my purpose?
How can I parse this json efficiently with Jackson? How can I skip those 18 elements and jump to next array for better performance?
Edit: (Solution)
Jackson and GSon both works in almost in the same mechanism (incremental mode, since content is read and written incrementally), I am switching to GSON as it has a function skipValue() (pretty appropriate with name). Although Jackson's nextToken() will work like skipValue(), GSON seems more flexible to me. Thanks #Kowser bro for his recommendation, I came to know about GSON before but somehow ignored it. This is my working code:
reader.beginArray();
while (reader.hasNext()) {
reader.beginArray();
int a = reader.nextInt();
int b = reader.nextInt();
String c = reader.nextString();
int d = reader.nextInt();
System.out.println(a + " " + b + " " + c + " " + d);
while (reader.hasNext())
reader.skipValue();
reader.endArray();
}
reader.endArray();
reader.close();

Answer 1

This is for Jackson
Follow this tutorial.
Judicious use of jasonParser.nextToken() should help you.
while (jasonParser.nextToken() != JsonToken.END_ARRAY) { // might be JsonToken.START_ARRAY?
The pseudo-code is
find next array
read values
skip other values
skip next end token
This is for gson.
Take a look at this tutorial. Consider following second example from the tutorial.
Judicious use of reader.begin* reader.end* and reader.skipValue should do the job for you.
And here is the documentation for JsonReader