How to assign to String[] from StringBuffer in a loop?

Question

Hi all,
public class Test {
public String[] getSJ() 
        String[]    jg;
        String[]    jig;
        String[]    tg;
        String[]    result;
        Date startTime;
        StringBuffer buf = new StringBuffer();
        int i;
        int j;
        int k = -1;
jg = {"g1", "g2"};
for( i=0; i < jg.length; i++ )
         jig = {"1", "2", "3"};
         for( j=0; i < jig.length; j++, k++ )
               buf.append( jg[i] ).append( ":" );                                      
               buf.append( jig[j] ).append( ":" );   
               buf.append( Date() );    
               result[k] = buf.toString();
               buf = null;
}I want to add to result string array by assigning from buf which is StringBuffer in a loop. But what happens after buf = null??
Will the added String be gone?
Or should I just do:
buf = "";
and continue with the loop and the string objects will be preserved? But isn't result just an array of references?
Many thanks,

Answer 1

I am not sure I understand correctly. Here is a test program (in real program I call APIs from a library which returns String[] for jg and for jig, i.e they are changing in the loop in runtime.
I tried to put together test program:
import java.util.*;
public class Test {
     public void Test() {
public String[] getSJ()
        String[] jg = {"g1", "g2"};
        String[] jig = {"1", "2", "3"};
        String[]    result = new String[50];
        StringBuffer buf = new StringBuffer();
        int i;
        int j;
        int k = 0;
for( i=0; i < jg.length; i++ )
         for( j=0; i < jig.length; j++, k++ )
               buf.append( jg[i] )
                  .append( ":" )
                  .append( jig[j] )
                  .append( ":" )
                  .append( new Date() );
               result[k] = buf.toString();
               buf = null;
   return result;
public static void main( String[] args ) {
    Test   t = new Test();
    String[] res = t.getSJ();
    for( int i=0; i<res.length; i++ ) {
     System.out.println( res[i] );
}but when I run it fails in this statement:
buf.append( jg[i] )
                  .append( ":" )
                  .append( jig[j] )
                  .append( ":" )
                  .append( new Date() );Exception in thread main
java.lang.NullPointerException
java.lang.String[] Test.getSJ()
Test.java:24
void Test.main(java.lang.String[])
Test.java:38
Wierd!?
And if I change to:
buf.setLength(0);
then it fails with this error:
Exception in thread main
java.lang.ArrayIndexOutOfBoundsException: 3
        java.lang.String[] Test.getSJ()
                Test.java:24
        void Test.main(java.lang.String[])
                Test.java:38Also, I would like not to have to allocate like in:
String[] result = new String[50];
because I do not know how many different Strings in array will be returned by API. Is it possible to dynamically adjust
String[] result
somehow?
Many thanks,