Compare two string arrays using arraylist

Question

I want to compare two string arrays A, B. I want to return and/or display the elements unique to A, B and those which are in both A & B. I called my method as shown below, but I get wrong results. How to fix it ?

A = 1,2,3,4,5;
B = 1,2;
compareStringArray(A,B, true);// true means print results

Results -

--Elements in ONLY A - 

3, 5

--Elements in ONLY B - 


--Elements in both A & B - 

2

Code-

public static ArrayList<ArrayList<String>> compareStringArray(
        String[] arrayA, String[] arrayB, boolean display) {

    ArrayList<ArrayList<String>> results = new ArrayList<ArrayList<String>>();
    ArrayList<String> ara = new ArrayList<String>(Arrays.asList(arrayA));
    ArrayList<String> arb = new ArrayList<String>(Arrays.asList(arrayB));
    ArrayList<String> common = new ArrayList<String>();

    for(String s : ara){
        if (arb.contains(s)) {
            common.add(s);
        }// if

    }//for

    for(String s: common){
        if (ara.contains(s)) {
            ara.remove(s);
        }// if

        if (arb.contains(s)) {
            arb.remove(s);
        }// if

    }//for


    results.add(ara);
    results.add(arb);
    results.add(common);

    if (display == true) {

        ArrayList<String> als = null;

        als = results.get(0);
        System.out.println("\n--Elements in ONLY A - \n");
        printArrayListOfStringAsCSV(als);

        als = results.get(1);
        System.out.println("\n--Elements in ONLY B - \n");
        printArrayListOfStringAsCSV(als);

        als = results.get(2);
        System.out.println("\n--Elements in both A & B - \n");
        printArrayListOfStringAsCSV(als);

    }// if

    return results;

}// compare

use nested loop ,in first time choose the first arg of arr1 and go through next arr which is arr2 — Mostafa Jamareh
– Mostafa Jamareh, Commented Dec 7, 2013 at 21:03
Can we see what results you are getting? Possible .contains(String) does not work for the same reason you use .equals() to compare strings and not == but I could be way off on that — ghostbust555
– ghostbust555, Commented Dec 7, 2013 at 21:04
@ghostbust555 - looks like you did not notice. The results have already been given ! — Trojan.ZBOT
– Trojan.ZBOT, Commented Dec 7, 2013 at 21:05
Oh wow you are correct. I read too quickly and assumed those were the desired results not the current reuslts — ghostbust555
– ghostbust555, Commented Dec 9, 2013 at 17:38

Elliott Frisch · Accepted Answer · 2013-12-07 21:10:14Z

1

Your code is working on my machine (I had to fix main, and implement printArrayListOfStringAsCSV so tsk-tsk) -

public static void main(String[] args) {
  String[] A = { "1", "2", "3", "4", "5" };
  String[] B = { "1", "2" };
  compareStringArray(A, B, true);
}

public static void printArrayListOfStringAsCSV(
    List<String> al) {
  for (int i = 0; i < al.size(); i++) {
    if (i != 0) {
      System.out.print(", ");
    }
    System.out.print(al.get(i));
  }
  System.out.println();
}

And I get this output (which looks 100% to me).

--Elements in ONLY A - 

3, 4, 5

--Elements in ONLY B - 



--Elements in both A & B - 

1, 2

answered Dec 7, 2013 at 21:10

Elliott Frisch

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3 Comments

Trojan.ZBOT Over a year ago

Yes, my stupidity :( . It was a problem with my printArrayListOfStringAsCSV method. Old method - public static void printArrayListOfStringAsCSV(ArrayList<String> results){ String csv = ""; int size = results.size(); if(size > 1){ int lastIdx = size - 1; for(int i = 0; i < lastIdx-1; i++){ csv = csv + results.get(i) + ", "; } csv = csv + results.get(lastIdx); System.out.println(csv); }//if }//print

Trojan.ZBOT Over a year ago

in the for loop, lastIdx-1 is to be replace by lastIdx-1.

Trojan.ZBOT Over a year ago

btw, i think that using if check for comma is a not good. Iterate up to last index and then print last element after that.

Alaychem goes to Codidact · Accepted Answer · 2013-12-07 21:17:01Z

1

It probebly means that the problem is in printArrayListOfStringAsCSV(). Look into it...

answered Dec 7, 2013 at 21:17

Alaychem goes to Codidact

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1 Comment

Trojan.ZBOT Over a year ago

yeah, my stupidity. i never thought i could make a mistake there :(

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