How to remove the last comma when I print out the index of arraylist

Question

List<String> list1 = new ArrayList<String>(words.length);
List<String> list2 = new ArrayList<String>(word.length);    
for(String x: list1){
        for(String y: list2){
            if(x.equalsIgnoreCase(y)){
               System.out.print(list1.indexOf(x) +" "+ ",");
            }
        }
    } 

For this function, after run it, the output will be 2,5,7....9, My question is how to remove the last comma?

Answer 1

I would print the comma at the start, something like this -

boolean first = true;
for(String x: list1){
    for(String y: list2){
        if(x.equalsIgnoreCase(y)){
           if (first) {
               first = false;
           } else {
               System.out.print(", "); // <-- or " ," if you prefer.
           }
           System.out.print(list1.indexOf(x));
        }
    }
}

Answer 2

You're going to have to figure out when the last item has been printed.

You can either do this by iterating through the list first and figuring out where the last comma should be, or you can build the whole String using StringBuilder and then take the comma of when you're done.

Alternatively, you could put the comma before the word for every word except the first one.

Answer 3

One solution is using loops with control over indexes:

int i,j;
for(i = 0;i < x.size();i++){
     for(j = 0;j < y.size() - 1; j++){
         if(list1.get(i).equalsIgnoreCase(list2.get(j))) {
              System.out.print(list1.indexOf(x) +" "+ ",");
         }
     }
     if(list1.get(i).equalsIgnoreCase(list2.get(j))) {
          System.out.print(list1.indexOf(x));
     }
} 

Answer 4

Use Iterator to check if there still next elements in your list.

System.out.print(list1.indexOf(x) +" ");
if(itr.hasNext()) {
    System.out.print(" ,"); // print the comma if there still elements
}

Answer 5

Just for completeness, here it is in Java 8:

final String joined = list1.stream().
        flatMap(s -> list2.stream().filter(y -> s.equalsIgnoreCase(y))).
        mapToInt(s -> list1.indexOf(s)).
        mapToObj(Integer::toString).
        collect(Collectors.joining(", "));

Answer 6

You could simply remove the last comma after building the string

Build the string:

StringBuilder output = new StringBuilder();
for(String x: list1){
  for(String y: list2){
     if(x.equalsIgnoreCase(y)){
        output.append(list1.indexOf(x) +" "+ ",");
     }
   }
}

Print with last comma removed:

System.out.println(output.substring(0, output.lastIndexOf(",")));

Answer 7

str = str.replaceAll(", $", "");

Answer 8

That's easy, do it this way:

Boolean b = false;
for(String x: list1){
    for(String y: list2){
        if(x.equalsIgnoreCase(y)){
           System.out.print((b ? "," : "") + list1.indexOf(x));
           b = true;
        }
    }
}