Java - Write code to replace substring only Once

Requirements

Write code to replace substring only Once

Demo

//package com.book2s;

public class Main {
    public static void main(String[] argv) {
        String template = "book2s.com";
        String placeholder = "o";
        String replacement = "O";
        System.out.println(replaceOnce(template, placeholder, replacement));
    }/*from w w  w. j  av  a2 s .  c  o  m*/

    public static String replaceOnce(String template, String placeholder,
            String replacement) {
        int loc = template == null ? -1 : template.indexOf(placeholder);
        if (loc < 0) {
            return template;
        } else {
            return new StringBuffer(template.substring(0, loc))
                    .append(replacement)
                    .append(template.substring(loc + placeholder.length()))
                    .toString();
        }
    }

    public static String toString(Object[] array) {
        int len = array.length;
        if (len == 0)
            return "";
        StringBuffer buf = new StringBuffer(len * 12);
        for (int i = 0; i < len - 1; i++) {
            buf.append(array[i]).append(", ");
        }
        return buf.append(array[len - 1]).toString();
    }
}

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