替换字符串中的单个字符

您几乎做到了，只需在循环中添加一个计数器即可：

int num2replace = keyboard.nextInt();int count = 0;for (int i = 0; i < bLength; i++) {    if (baseString.charAt(i) == char2replace.charAt(0)) {        count++;        if (count == num2replace){ baseString = baseString.substring(0, i) +         secondChar + baseString.substring(i + 1); break;        }    }    if (char2replace.length() > 1) {//you need move this out of loop        System.out.println("Error you can only enter one character");    }}System.out.println(baseString);