StringBuilder 上的 IndexOutOfBoundException

Question

我正在尝试使用以下代码将 pi 替换为 *pi，但它抛出了完全意外的异常。匹配器如何查看大于字符串长度的索引？

private void makeEvaluationStringExpressionMXParserCompliant() {
        Pattern multiply = Pattern.compile(mContext.getString(R.string.string_multiply));
        Pattern pi = Pattern.compile(mContext.getString(R.string.string_pie));
        Pattern e = Pattern.compile(mContext.getString(R.string.string_e));

        Log.e("wingoku", "pi: "+ pi.toString() + " completeString: "+ mEvaluationStringExpressionBuilder.toString());

       replaceAll(mEvaluationStringExpressionBuilder, pi, "*pi");
    }

    private void replaceAll(StringBuilder sb, Pattern pattern, String replacement) {
        Matcher m = pattern.matcher(sb);
        int start = 0;
        while (m.find(start)) {
            sb.replace(m.start(), m.end(), replacement);
            start = m.start() + replacement.length();
        }
    }

异常：

 java.lang.IndexOutOfBoundsException: start=3; length=2
                                                     at java.util.regex.Matcher.find(Matcher.java:339)
                                                     at com.app.calculator.utils.StringExpressionFactory.replaceAll(StringExpressionFactory.java:68)
                                                     at com.app.calculator.utils.StringExpressionFactory.makeEvaluationStringExpressionMXParserCompliant(StringExpressionFactory.java:61)
                                                     at com.app.calculator.utils.StringExpressionFactory.createExpression(StringExpressionFactory.java:31)

Answer 1

问题是您传递的初始索引超出了您试图在其中查找匹配项的字符串的长度。方法文档说明如下：

Throws: IndexOutOfBoundsException - If start is less than zero or if start is greater than the length of the input sequence.

您需要添加检查以查看初始索引是否有效：

while (start < sb.length() && m.find(start)) {
    sb.replace(m.start(), m.end(), replacement);
    start = m.start() + replacement.length();
}

Answer 2

你的起始位置有误。你可以检查一下。以下源代码：

public static void replaceAll(StringBuilder sb, Pattern pattern, String replacement) {
Matcher m = pattern.matcher(sb);
while(m.find()) {
    sb.replace(m.start(), m.end(), replacement);
}

}

你最好写个代码。你不需要做 replaceAll Function

 StrBuilder replaceAll(char search, char replace)

在整个构建器中用替换字符替换搜索字符。

https://commons.apache.org/proper/commons-lang/javadocs/api-3.1/org/apache/commons/lang3/text/StrBuilder.html#replaceAll(java.lang.String,%20java.lang.String)

StringBuilder 上的 IndexOutOfBoundException

IndexOutOfBoundException on StringBuilder

java

stringbuilder

indexoutofboundsexception