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1 package com.db4o.f1.chapter1;
2
3 import com.db4o.*;
4 import com.db4o.f1.*;
5 import com.db4o.query.*;
6
7 public class NQExample extends Util {
8
9 public static void main(String  [] args) {
10 ObjectContainer db=Db4o.openFile(Util.YAPFILENAME);
11 try {
12 storePilots(db);
13 retrieveComplexSODA(db);
14 retrieveComplexNQ(db);
15 retrieveArbitraryCodeNQ(db);
16 clearDatabase(db);
17 }
18 finally {
19 db.close();
20 }
21 }
22
23 public static void storePilots(ObjectContainer db) {
24 db.set(new Pilot("Michael Schumacher",100));
25 db.set(new Pilot("Rubens Barrichello",99));
26 }
27
28 public static void retrieveComplexSODA(ObjectContainer db) {
29 Query query=db.query();
30 query.constrain(Pilot.class);
31 Query pointQuery=query.descend("points");
32 query.descend("name").constrain("Rubens Barrichello")
33 .or(pointQuery.constrain(new Integer (99)).greater()
34 .and(pointQuery.constrain(new Integer (199)).smaller()));
35 ObjectSet result=query.execute();
36 listResult(result);
37 }
38
39 public static void retrieveComplexNQ(ObjectContainer db) {
40 ObjectSet result=db.query(new Predicate() {
41 public boolean match(Pilot pilot) {
42 return pilot.getPoints()>99
43 && pilot.getPoints()<199
44 || pilot.getName().equals("Rubens Barrichello");
45 }
46 });
47 listResult(result);
48 }
49
50 public static void retrieveArbitraryCodeNQ(ObjectContainer db) {
51 final int[] points={1,100};
52 ObjectSet result=db.query(new Predicate() {
53 public boolean match(Pilot pilot) {
54 for(int i=0;i<points.length;i++) {
55 if(pilot.getPoints()==points[i]) {
56 return true;
57 }
58 }
59 return pilot.getName().startsWith("Rubens");
60 }
61 });
62 listResult(result);
63 }
64
65 public static void clearDatabase(ObjectContainer db) {
66 ObjectSet result=db.get(Pilot.class);
67 while(result.hasNext()) {
68 db.delete(result.next());
69 }
70 }
71 }
72 |
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Java API By Example, From Geeks To Geeks.