Java 8 stream - merge collections of objects sharing the same Id

Question

I have a collection of invoices :

class Invoice {
  int month;
  BigDecimal amount
}

I\'d like to merge these invoices, so I get one invoice pe

Answer 1

I think if your application do not support lambda than this might be a suitable answer eg (Android minSdkVersion=16 do not support lambda)

public static List mergeAmount(List invoiceList) {
 List newInvoiceList = new ArrayList<>();
  for(Invoice inv: invoiceList) {
    boolean isThere = false;
     for (Invoice inv1: newInvoiceList) {
      if (inv1.getAmount() == inv.getAmount()) {
         inv1.setAmount(inv1.getAmoount()+inv.getAmount());
         isThere = true;
         break;
       }             
     }
    if (!isThere) {
        newInvoiceList.add(inv);
    } 
 }
  return newInvoiceList;
}