Question

我有文本文件，其中包含保存在字符串中的属性。这些字符串有这样的模式：

[attributeName]:[value]

我无法概括[value]，因为它可能是任何原始数据类型。保存有效值不是我关注的问题，因为它取决于用户必须加载哪个属性。不会经常加载相同的文件。

现在我有两个问题：

1）由于某种原因，创建这些文件的程序有时会在：某些属性周围添加空格，[value]也可能包含空格，所以我必须摆脱那些

2）使这些属性的阅读更具性能：

我想出了这个方法：

public String getAttribute(File file, String attribute)
{
    try
    {
        BufferedReader reader = new BufferedReader(new FileReader(file), 1024);
        String line;
        Pattern p = Pattern.compile(Pattern.quote(attribute), Pattern.CASE_INSENSITIVE);
        while ((line = reader.readLine()) != null)
        {
            int i = line.indexOf(":");

            if(line.charAt(i-1) == ' ')
                line = line.substring(0,i-2) + line.substring(i);

            if(line.charAt(i+1) == ' ')
                line = line.substring(0,i) + line.substring(i+2);

            if (p.matcher(line).find())
            {
                return line.replace(attribute, "").trim();
            }

        }
    } catch (IOException e)
    {
        e.printStackTrace();
    }

    return null;
}

但是，这个方法可能是我的应用程序调用最多的方法之一，所以我不能让它像现在这样无法使用，谢谢你的帮助！

Answer 1

我修改了代码以找到合适的行。检查下面的示例代码。
如果这些文件中有很多文件和属性，您可以考虑在代码中保存某个对的attribute = value。在示例代码中，我使用Table库中的guava接口提供了非常原始的缓存。

示例代码：

# guava library
import com.google.common.collect.Table;
import com.google.common.collect.HashBasedTable;

# apache commons lang
import static org.apache.commons.lang.StringUtils.startsWithIgnoreCase;
# apache commons io
import static org.apache.commons.io.IOUtils.closeQuietly;
[...]
# very primitive cache implementation. To find a value in table you have to
# pass row and column keys. In this implementation row is equal to file
# absolute path (because you can have 2 files with the same name) and column
# is equal to attribute name.
# If you have a lot of files and attributes probably you will have to clear
# from time to time the cache otherwise you will get out of memory
private static final Table<String, String, String> CACHE = HashBasedTable.create();
[...]
public String getAttribute(File file, String attribute) {
    # get value for the given attribute from the given file
    String value = CACHE.get(file.getAbsolutePath(), attribute);        

    # if cache does not contain value, method will read value from file
    if (null == value) {
        BufferedReader reader = null;
        String value = null;

        try {
            reader = new BufferedReader(new FileReader(file), 1024);
            String line;

            while ((line = reader.readLine()) != null) {
                # From your description I understood that each line in file
                # starts with attribute name
                if (startsWithIgnoreCase(line, attribute) {
                    # if we found correct line we simple split it by ':'
                    String[] array = line.split(":");

                    # this is to ensure that line contains attribute name
                    # and value
                    if (array.length >= 2) {
                        # we found value for attribute and we remove spaces
                        value = array[1].trim();
                        # we put value to the cache to speed up finding
                        # value for the same attribute in the future
                        CACHE.put(file.getAbsolutePath(), attribute, value);
                        break;
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            # you should always close 
            closeQuietly(reader);
        }
    }

    return value;
}

使用模式从字符串中获取值

1 个答案: