Hello All,
I have been playing around with ArrayList and encounter this kind of
behavior:
import java.util.ArrayList;
public class TestArrayList1 {
static ArrayList<String[]> arlQueryResult = new
ArrayList<String[]>(10);
static String[] strQueryResult = new String[4];
static String[] strQueryResult2 = new String[4];
public static void main(String[] args) {
strQueryResult[0] = "a";
strQueryResult[1] = "b";
strQueryResult[2] = "c";
strQueryResult[3] = "d";
arlQueryResult.add(strQueryResult);
strQueryResult[0] = "e";
strQueryResult[1] = "f";
strQueryResult[2] = "g";
strQueryResult[3] = "h";
arlQueryResult.add(strQueryResult);
for (int i = 0; i< arlQueryResult.size(); i++){
for (int j = 0; j<=3; j++){
String str = arlQueryResult.get(i)[j];
System.out.println("Result " + i + j + ": " +
str);
}
}
}
}
The output is not "a b c d e f g h" as expected but:
Result 00: e
Result 01: f
Result 02: g
Result 03: h
Result 10: e
Result 11: f
Result 12: g
Result 13: h
I have to use the array of strQueryResult2 to store "e f g h" and
arlQueryResult.add(strQueryResult2); to obtain this output:
Result 00: a
Result 01: b
Result 02: c
Result 03: d
Result 10: e
Result 11: f
Result 12: g
Result 13: h
Thus, the questions are:
1. Why can't I reuse the array of strQueryResult to add a new element in
the ArrayList of arlQueryResult?
2. What is the best practice to add a new element of Array in ArrayList
in this case, if I want to put the algorithm in a loop and perform the
arlQueryResult.add(...) many times as the content of the array of
strQueryResult varies?
Thanks for the advice,
Patrick
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