How to implement the template(replacing string with the element of list) in java.

Question

I am developing an application in which I came across the requirement where I need to do the replacement of identifying words with the strings ie replacing the actual data in templates. In this I am getting the data from an arraylist and for that I have implemented the following solution.

List<String> abc = new ArrayList<String>();
        abc.add("willy brown");
        abc.add("jamster");
        String message="//$^$// has commented on //$^$// .";
        String messages[] = message.split(" ");
        StringBuffer finalMessage = new StringBuffer();
        for(int i=0,j=0; i<messages.length && j<=abc.size(); i++){
            System.out.println("messages : " + messages[i]);
            if(messages[i].equals("//$^$//")){
                messages[i] = abc.get(j);
                System.out.println("after changes " +messages[i]);
                j++;
            }
            finalMessage.append(messages[i] +" ");
        }
        System.out.println("final message: " + finalMessage);

I just want to know if there is any better way to implement this and also if there is any vulnerability in this.

Answer 1

I would use MessageFormat.format for this:

    List<String> abc = new ArrayList<String>();
    abc.add("willy brown");
    abc.add("jamster");

    String message = "{0} has commented on {1}";
    String finalMessage = MessageFormat.format(message, abc.toArray(new String[abc.size()]));
    System.out.println(finalMessage);

Answer 2

You can use the built in String and StringBuffer methods to perform this task without having to break apart the message into an array. I also suggest extracting your field identifier into a separate variable. God forbid you miss-type it somewhere!

    String fieldIdentifier = "//$^$//";

    List<String> abc = new ArrayList<>();
    abc.add("willy brown");
    abc.add("jamster");

    String message= fieldIdentifier + " has commented on "  + fieldIdentifier + ".";
    StringBuffer finalMessage = new StringBuffer(message);

    int fieldCount = 0;

    while(finalMessage.indexOf(fieldIdentifier) > -1) {
        int index = finalMessage.indexOf(fieldIdentifier);
        finalMessage = finalMessage.replace(index, index + fieldIdentifier.length(), abc.get(fieldCount));

        fieldCount++;
    }

    System.out.println("final message: " + finalMessage);

Edit: using StringBuffer for these kinds of operations is highly preferable, since it is mutable and much faster than using String.