如何实现 SAX 处理程序的 character() 函数以最小化内存使用？

发布于 2024-10-20 12:44:27 字数 896 浏览 1 评论 0原文

我正在我的 Android 应用程序中实现 java SAX 解析器。

我已经让一切正常工作，但我正在尝试优化一小部分，该部分会占用更多所需的内存。

这是我当前（我知道效率很低）DefaultHandler 的character() 函数。

String currentText = "";

    @Override
public void characters(char[] ch, int start, int length)
{
    if(currentText.length() > 0)
    {
        currentText = currentText.concat(new String(ch, start, length));
    }else
    {
        //Takes half as much memory as concating to empty string
        currentText = new String(ch, start, length);
    }
}

基本上，当 SAX 遇到元素内的文本时，就会调用此函数。值得注意的是，整个文本不能保证立即被解析，因此新字符必须附加到 currentText 中当前的任何文本中（请注意，currentText 在每个元素的末尾设置为“”）。

我只是将这段代码放在一起使其工作，这样我就可以测试解析器的其余部分，但这需要优化。

关于如何实现这一点以使用尽可能少的内存有什么建议吗？

原文

I'm implementing a java SAX parser in my Android app.

I've got everything working, but I'm trying to optimize one little piece that is sucking up a lot more memory that is needed.

This is my current (and quite inefficient I know) implementation of the DefaultHandler's character() function.

String currentText = "";

    @Override
public void characters(char[] ch, int start, int length)
{
    if(currentText.length() > 0)
    {
        currentText = currentText.concat(new String(ch, start, length));
    }else
    {
        //Takes half as much memory as concating to empty string
        currentText = new String(ch, start, length);
    }
}

Basically, this function is called when SAX encounters text inside an element. It's important to note though that the entire text is not guaranteed to be parsed at once, so the new characters must be appended to whatever text is currently in currentText (note that currentText is set to "" at the end of every element).

I just threw this code together to make it work so I could test the rest of my parser, but this needs to be optimized.

Any suggestions on how I can implement this to use as little memory as possible?

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月寒剑心 2024-10-27 12:44:27

使用 StringBuilder。

StringBuilder currentText = new StringBuilder();

@Override
public void characters(char[] ch, int start, int length)
{
   currentText.append(ch, start, length);
}

稍后您可以通过调用 currentText.toString() 来获取全文。

更新以模拟修剪：

@Override
public void characters(char[] ch, int start, int length)
{
   if(length == 0) return;
   int end = (start + length) - 1;
   while(char[start] <= '\u0020')
   {
       if(start == end) return;
       start++;
       length--;
   }
   while(char[end] <= '\u0020')
   {
       if(end == start) return;
       length--;
       end--;
   }
   currentText.append(ch, start, length);
}

Use a StringBuilder.

StringBuilder currentText = new StringBuilder();

@Override
public void characters(char[] ch, int start, int length)
{
   currentText.append(ch, start, length);
}

Later on you can get the full text by calling currentText.toString().

Update to simulate a trim:

@Override
public void characters(char[] ch, int start, int length)
{
   if(length == 0) return;
   int end = (start + length) - 1;
   while(char[start] <= '\u0020')
   {
       if(start == end) return;
       start++;
       length--;
   }
   while(char[end] <= '\u0020')
   {
       if(end == start) return;
       length--;
       end--;
   }
   currentText.append(ch, start, length);
}

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