Adding empty or null on arraylist in java

Question

I am trying to search account numbers on an excel file, which in return, i will get a 'total amount due' if the account number exists in the sheet. I can scan using this code, however, I get error if the account number does not exists in the sheet.

for(int i = 0; i < accno.size(); i++){
    for(int j = rowAccNo1+1; j < row.getRowNum(); j++){
           srcaccno = formatter.formatCellValue(sheet.getRow(j).getCell(0));
           totalamt = formatter.formatCellValue(sheet.getRow(j).getCell(10));

          if(accno.get(i).contains(srcaccno)){
                  totalamountdue.add(i, totalamt);
          }
      }
  }

Edit: Hi, I am using Apache POI.

I declared accno as below:

static ArrayList<String> accno = new ArrayList<String>();

and I am getting this error. perhaps Java can't find the account number that's why he throws this. But I do not know if I can add an empty or null on my arraylist.

at java.util.ArrayList.rangeCheckForAdd(Unknown Source) at java.util.ArrayList.add(Unknown Source) at com.joven.DataExtractionTool.App.compareMastertoSourceABC(App.java:372) at com.joven.DataExtractionTool.App.main(App.java:78) at com.joven.DataExtractionTool.AppTest.testApp(AppTest.java:17) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at junit.framework.TestCase.runTest(TestCase.java:154) at junit.framework.TestCase.runBare(TestCase.java:127) at junit.framework.TestResult$1.protect(TestResult.java:106) at junit.framework.TestResult.runProtected(TestResult.java:124) at junit.framework.TestResult.run(TestResult.java:109) at junit.framework.TestCase.run(TestCase.java:118) at junit.framework.TestSuite.runTest(TestSuite.java:208) at junit.framework.TestSuite.run(TestSuite.java:203) at org.eclip se.jdt.internal.junit.runner.junit3.JUnit3TestReference.run(JUnit3TestReference.java:131) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

Thank you for your response!

What I really like to do is that, if accno exists in the sheet, get totalamountdue. if it does not exists, put blank on totalamountdue so that it will display blank if i output the arraylist in console.

Answer 1

Your problem come from this

if(accno.get(i).contains(srcaccno)){
     totalamountdue.add(i, totalamt); // ########
}

Since you add the total to a specific index in the list (the one corresponding to the account list), you need to insert a "default" value if you don't find the account in the sheet. If you do not, you will have a different length between the account list and the total list. Meaning that you try to add a value to far (out of bounds exception).

Actually, there is a much easier way (don't know why I didn't think first)

Before you even start to search into the sheet, insert a null value

totalamountdue.add(null);

Then, in the search loop, if you find a value replace this null with the total found.

if(accno.get(i).contains(srcaccno)){
     totalamountdue.set(i, totalamt); // use SET to replace the value at a specific index.
}

The full loop

totalamoutdue.add(null); //will insert at the end, i.
for(int j = rowAccNo1+1; j < row.getRowNum(); j++){
      srcaccno = formatter.formatCellValue(sheet.getRow(j).getCell(0));
      if(accno.get(i).contains(srcaccno)){
              totalamt = formatter.formatCellValue(sheet.getRow(j).getCell(10)); //No need to get the value if it is not the account you want
              totalamountdue.set(i, totalamt);
              break; //Break the current for loop, IF there is no need to read further
      }
  }

Answer 2

I assume something is wrong with iterating over those lists, so I simplified code - hope it will work.

Map<String, BigDecimal> accountsDue = new HashMap<>();

for (int j = rowAccNo1 + 1; j < row.getRowNum(); j++) {
  String srcaccno = formatter.formatCellValue(sheet.getRow(j).getCell(0));
  BigDecimal amountDue = formatter.formatCellValue(sheet.getRow(j).getCell(10));
  if (accno.contains(srcaccno)) {
    putOrIncreaseDue(srcaccno, amountDue, accountsDue);
  }
}

private void putOrIncreaseDue(String srcaccno, BigDecimal amountDue, Map<String, BigDecimal> accountsDue) {
  if (accountsDue.containsKey(srcaccno)) {
    amountDue.add(accountsDue.get(srcaccno));
  }
  accountsDue.put(srcaccno, amountDue);
}