Dynamically name arrays

[KTSAIC Thomas]

Hey all,

Strange one for you...

I have a table which will contain generic columns like so:

PARAM0_NAME
PARAM0_TYPE
PARAM0_VALUE
PARAM1_NAME
PARAM1_TYPE
PARAM1_VALUE

etc, etc...up to 9. What I would like to do is dynamically create the arrays for each of these columns at runtime, something like:

...
int i = 0;

while ( i < 10; i++ ){
String[] strParam<i>_name = new String[noReccount]
String[] strParam<i>_type = new String[noReccount]
String[] strParam<i>_value = new String[noReccount]
}
...

Any thoughts on whether this is feasible? I guess I just don't want to have to type it all out (I'm being lazy!)

[William Brogden]

If you want a variable number of String[] that can be located by names made up on the fly, I suggest you look into the "collections" API in the java.util package. Specifically the various Map implementations.
Bill

[Nathan Pruett]

Why use Strings? Wouldn't it be better to make a small Parameter class with name, value, and type properties and create arrays of those?

(Warning - the following code hasn't been tested/compiled/anything - it's just out of my head, and is to serve as a general outline of the process...

// Get the JDBC Connection, Statement, etc.
 
// PARAM_COLS holds the number of columns each parameter uses, and is 
// used as the step value when iterating through the query.
final int PARAM_COLS = 3;
 
// MAX_PARAM holds the maximum parameter number
final int MAX_PARAM = 10;
 
// params holds the Parameter objects as they are built.
Parameter[] params = new Parameter[MAX_PARAM];
 
ResultSet rs = statement.executeQuery("SELECT PARAM0_NAME, PARAM0_TYPE, PARAM0_VALUE, ... FROM PARAM_TABLE");
 
// paramCount is used to go to the next parameter while iterating through
// the query, and is also used to determine the last used parameter.
int paramCount = 0;
 
// moreValues signals when there are no more parameter entries in the query.
boolean moreValues = true;
 
while( moreValues && paramCount < MAX_PARAM ) {
    int currentIndex = paramCount * PARAM_COLS;
    String name = rs.getString(currentIndex + 1);
    String type = rs.getString(currentIndex + 2);
    String value = rs.getString(currentIndex + 3);
    if ( name == null || name.trim().equals("") ) {
        moreValues = false;
    } else {
        params[paramCount] = new Parameter(name, value, type);
        paramCount++;
    }
}
 
// final "cleanup" of the array length
if (paramCount != MAX_PARAM) {
    Parameter[] newParams = new Parameter[paramCount];
    System.arraycopy(params, 0, newParams, 0, paramCount);
    params = newParams;
}

I don't see anything specific to JSPs in this question... moving to Java Programming in General (Intermediate)

[Layne Lund]

I agree. You should create a class with fields that correspond to the columns in your table. Then you just have to manage a single array with instances of this class.

HTH

Layne