Java StringBuilder 不追加字符串

Question

我在我的项目中使用 StringBuilder。当我附加 char 时一切正常，但是当我尝试附加字符串“8（”或“）”或“”时，它保持为空“”。示例（已编辑）：

    int length = number.length();
    CharSequence sequence = number.subSequence(0,length);
    StringBuilder stringBuilder = new StringBuilder(17);
    for (int i = 0; i < length; i++){
        if (Pattern.matches("^[\d]$", String.valueOf(sequence.charAt(i)))){
            stringBuilder.append(sequence.charAt(i));
        }
    }
    sequence = stringBuilder.toString();
    stringBuilder = new StringBuilder(17);
    CharSequence s = "8 (";
    if (sequence.charAt(0) == 8 || sequence.charAt(0) == 7 || sequence.length() == 0){
        stringBuilder.append(s);
    }
    for (int i = 1; i < 11 && i < sequence.length(); i++){
        stringBuilder.append(sequence.charAt(i));
        if (i == 3){
            stringBuilder.append(") ");
        }
        if (i == 6 || i == 8){
            stringBuilder.append(' ');
        }
    }
    number.clear();
    number.clearSpans();
    number.append(stringBuilder.toString());

Answer 1

你的代码有问题

if (sequence.charAt(0) == 8 || sequence.charAt(0) == 7 ||

你需要比较字符而不是整数

if (sequence.charAt(0) == '8' || etc

Java StringBuilder 不追加字符串

Java StringBuilder does not append strings

java

stringbuilder