使用单个StringBuilder-抛出OutofmemeoryException [英] Using single StringBuilder - throws OutofmemeoryException

问题描述

像下面的代码一样，读取每一行并基于输入列表listValues进行串联.

do like the below code, to read each line and perform a concatenation based on an input list listValues.

BufferedReader br = null;
StringBuilder sb = new StringBuilder("");
InputStream in = new FileInputStream(new File(file));
br = new BufferedReader(new InputStreamReader(in), 102400);
for (String input; (input= br.readLine()) != null;) {
    for (int i = 0; i < listValues.size(); i++) {
        sb.append(input.substring(1, 5));
    }
    map.put(sb.toString(), someOtherValue);
    sb.delete(0, sb.length());
}

通过设置每次都删除内容来对每次迭代使用相同的StringBuilder.仍会抛出

Using the same StringBuilder for each iteration by setting deleting the contents each time. Still throws

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
at java.lang.String.substring(Unknown Source)

我犯了什么错误?

我已经按照 Bathsheba 的建议进行了更正. 但是现在抛出，

I have corrected as per Bathsheba's suggestion. But now throws,

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
at java.util.Arrays.copyOfRange(Unknown Source)
at java.lang.String.<init>(Unknown Source)
at java.io.BufferedReader.readLine(Unknown Source)
at java.io.BufferedReader.readLine(Unknown Source)

在for (String input; (input= br.readLine()) != null;) 现在出什么问题了?

at for (String input; (input= br.readLine()) != null;) What's the problem now?

推荐答案

在紧循环中使用substring是不明智的，因为它会创建很多字符串，直到以后才可能被垃圾回收.

Using substring within a tight loop is ill-advised since it will create many strings that may not be garbage collected until later.

您的解决方案是使用charAt并将char附加到StringBuilder实例:

A solution in your case would be to use charAt and append the chars to the StringBuilder instance:

for (int j = 1; j <= 5; ++j){ /*ToDo - check the loop bounds*/
    sb.append(input.charAt(j)); /*StringBuilder has an overload for `char` insertion*/
}

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