method criteriaFind

[Allen Chan]

Hi all,
here is the criteriaFind I did, I have an error when I do

rv[j++] = new DataInfo(j, description,values);

/******************/
// criteria format
//FlightNO='PA001'[,Destination='JFK',..]
public synchronized DataInfo[] criteriaFind(String criteriaString) throws DatabaseException {
invariant();
try {
System.out.println("try finding"); //###
//##########
//tokenize and parse the criteria
StringTokenizer criteriaTokens = new StringTokenizer(criteriaString,",");
int tokenCount = criteriaTokens.countTokens();
System.out.println("tokencount="+tokenCount);
//the field need to be matched in each flight
//if need match, set to 1
int filedToMatch[] ={0,0,0,0};
String valuesToMacth[]={"", "", "", ""};
while (criteriaTokens.hasMoreTokens()){
//get the criteria pair and trim
String criteriaPair = criteriaTokens.nextToken().trim();
//System.out.println("nextToken="+criteriaPair);
int equalSignPos = criteriaPair.indexOf("=");
String criteria = criteriaPair.substring(0,equalSignPos);
//System.out.println("criteria=" + criteria);
int valueStartIndex = equalSignPos+2;
int valueStopIndex = criteriaPair.length()-1;
String criteriaValue = criteriaPair.substring(valueStartIndex,valueStopIndex);
//System.out.println("criteriavalue="+ criteriaValue);
if (criteria .equals("FlightNo")) {
filedToMatch[0] = 1;
valuesToMacth[0] = criteriaValue;
} else if (criteria.equals("Origin")) {
filedToMatch[1] = 1;
valuesToMacth[1] = criteriaValue;
} else if (criteria.equals("Destination")) {
filedToMatch[2] = 1;
valuesToMacth[2] = criteriaValue;
} else if (criteria.equals("Carrier")) {
filedToMatch[3] = 1;
valuesToMacth[3] = criteriaValue;
}
}
for (int i=0; i<4; i++){
System.out.println("filedToMatch" + i + "=" + filedToMatch[i]);

}
//##########
seek(1);
DataInfo[] rv = null;
String [] values = null;
boolean found = false;
int r;
int j=0;
for (r = 1; r <= recordCount; r++) {
values = readRecord();
System.out.println("search for record no." + r);
if (values != null) {
found = true;
for (int i=0; i<4; i++) {
//System.out.println("enter for loop");
if (filedToMatch[i] == 1){
//System.out.println("compare now");
found= found && (values[i].equals(valuesToMacth[i]));
//System.out.println("found= " + found);
}else{
//System.out.println(" skip compare");
}
}
}
//if(found) break;
if (found) {
System.out.println("I find it, yahhhhhh, yehhhhh "); //###
rv[j++] = new DataInfo(j, description, values);
System.out.println("OK");
}
}
/*
if (found) {
rv = new DataInfo(r, description, values);
System.out.println("I find it, yahhhhhh, yehhhhh "); //###
}
*/ return rv;
} catch (IOException e) {
throw new DatabaseException(UNEXPECTED + e);
}
}
/***************/

What is the fix for this?
Could someone tell me if the way to parse the criteria OK?
Thanks.

[jay denzel]

Hi Allen,
I would implement a more generic form of criteriaFind, because the assignment says that
the application should be extensible in the future.
I did my criteriaFind covering every column of the database schema.
E.g. you could pass a criteria like
flight='SA001',origin='SFO',destination='DEN',carrier='SpeedyAir',price='400',day='Sun',time='13:40',duration='20m',seats='50'
First I use the array dataInfo returns and look up any occurrence of the field name in the
criteria String, this way I get each seach criteria very easy (no StringTokinzer needed).
Then I build the mapping for column number to search criteria, which I put into a HashMap.
The resulting map looks e.g similar to this {3=DEN,1=SFO,0=SA001}.
I have a private method matchFind which takes the map as argument and returns a List.
Now I know exactly in which columns I have to search and the criteria for the specific column.
The rest is just looping through all records and comparing the columns and criterias which
I have in my map with the corresponding column and entry in the received record.
Doing it in this fashion I think is a more general approach to solving the problem and
it works with different database table schemas as well.
Hope this helps.
jay

[jay denzel]

One more thing to mention.
You can not dynamically resize arrays,
e.g.
DataInfo[] r = new DataInfo[x];
for (int i=0; i < 10; i++)
r[i] = new DataInfo( .. )
is not possible, that is why you get an error.
why not return a List
public synchronized List criteriaFind(...
and put the DataInfo objects into the List.
jay

[Allen Chan]

hi Jay,
Thank you very much for your reply. That is a good idea. However, still could not figure out how to use map (put criteria in map?), then how you do the compare?
Thanks again for your clue.