How to replace a set of tokens in a Java String?

Question

I have the following template String: "Hello [Name] Please find attached [Invoice Number] which is due on [Due Date]".

I also have String variables for name, invoice number and due date - what's the best way to replace the tokens in the template with the variables?

(Note that if a variable happens to contain a token it should NOT be replaced).

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EDIT

With thanks to @laginimaineb and @alan-moore, here's my solution:

public static String replaceTokens(String text,                                     Map<String, String> replacements) {     Pattern pattern = Pattern.compile("\\[(.+?)\\]");     Matcher matcher = pattern.matcher(text);     StringBuffer buffer = new StringBuffer();      while (matcher.find()) {         String replacement = replacements.get(matcher.group(1));         if (replacement != null) {             // matcher.appendReplacement(buffer, replacement);             // see comment              matcher.appendReplacement(buffer, "");             buffer.append(replacement);         }     }     matcher.appendTail(buffer);     return buffer.toString(); } 

Answer 1

I really don't think you need to use a templating engine or anything like that for this. You can use the String.format method, like so:

String template = "Hello %s Please find attached %s which is due on %s";  String message = String.format(template, name, invoiceNumber, dueDate); 

Answer 2

The most efficient way would be using a matcher to continually find the expressions and replace them, then append the text to a string builder:

Pattern pattern = Pattern.compile("\\[(.+?)\\]"); Matcher matcher = pattern.matcher(text); HashMap<String,String> replacements = new HashMap<String,String>(); //populate the replacements map ... StringBuilder builder = new StringBuilder(); int i = 0; while (matcher.find()) {     String replacement = replacements.get(matcher.group(1));     builder.append(text.substring(i, matcher.start()));     if (replacement == null)         builder.append(matcher.group(0));     else         builder.append(replacement);     i = matcher.end(); } builder.append(text.substring(i, text.length())); return builder.toString();