我正在学习如何使用Java处理文件。我有一个示例文件,其中包含密钥对及其值。我试图找到一个密钥对,如果匹配,那么输出文件将同时更新,密钥对及其值。我能够在输出文件中获取密钥对,但也无法获取值。 Stringbuilder可能在这里工作以追加字符串,但我不知道如何。
下面是我的输入和输出文件。
Input File:
born time 9 AM London -- kingNumber 1234567890 -- address: abc/cd/ef -- birthmonth: unknown
born time 9 AM Europe -- kingNumber 1234567890 -- address: abc/cd/ef -- birthmonth: december
Expected Output File:
kingNumber 1234567890 birthmonth unknown
kingNumber 1234567890 birthmonth unkbown
Current Output File:
kingNumber birthmonth
kingNumber birthmonth
我能够写密钥对(在这种情况下为“ kingNumber”和“ birthmonth”)来输出文件,但是我不确定该怎么做才能得到它的值。
String kn = "kingNumber:";
String bd = "birthmonth:";
try {
File f = new File("sample.txt");
Scanner sc = new Scanner(f);
FileWriter fw = new FileWriter("output.txt");
while(sc.hasNextLine()) {
String lineContains = sc.next();
if(lineContains.contains(kn)) {
fw.write(kn + "\n");
// This is where I am stuck. What
// can I do to get it's value (number in this case).
}
else if(lineContains.contains(bd)) {
fw.write(bd);
// This is where I am stuck. What
// can I do to get it's value (birthday in this case).
}
}
} catch (IOException e) {
e.printStackTrace();
}
答案 0 :(得分:0)
我编写了一个简单的解析器,它遵循您示例中的数据格式。 您将需要这样称呼它:
PairParser parser = new PairParser(lineContains);
然后您可以通过配对键从解析器获取价值 如何获得价值:
parser.getValue("kingNumber")
请注意,键没有尾随列字符。
解析器代码在这里:
package com.grenader.example;
import java.util.HashMap;
import java.util.Map;
public class PairParser {
private Map<String, String> data = new HashMap<>();
/**
* Constructor, prepare the data
* @param dataString line from the given data file
*/
public PairParser(String dataString) {
if (dataString == null || dataString.isEmpty())
throw new IllegalArgumentException("Data line cannot be empty");
// Spit the input line into array of string blocks based on '--' as a separator
String[] blocks = dataString.split("--");
for (String block : blocks)
{
if (block.startsWith("born time")) // skip this one because it doesn't looks like a key/value pair
continue;
String[] strings = block.split("\\s");
if (strings.length != 3) // has not exactly 3 items (first items is empty), skipping this one as well
continue;
String key = strings[1];
String value = strings[2];
if (key.endsWith(":"))
key = key.substring(0, key.length()-1).trim();
data.put(key.trim(), value.trim());
}
}
/**
* Return value based on key
* @param key
* @return
*/
public String getValue(String key)
{
return data.get(key);
}
/**
* Return number of key/value pairs
* @return
*/
public int size()
{
return data.size();
}
}
这是确保代码正常工作的单元测试
package com.grenader.example;
import com.grenader.example.PairParser;
import org.junit.Test;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.fail;
public class PairParserTest {
@Test
public void getValue_Ok() {
PairParser parser = new PairParser("born time 9 AM London -- kingNumber 1234567890 -- address: abc/cd/ef -- birthmonth: unknown");
assertEquals("1234567890", parser.getValue("kingNumber"));
assertEquals("unknown", parser.getValue("birthmonth"));
}
@Test(expected = IllegalArgumentException.class)
public void getValue_Null() {
new PairParser(null);
fail("This test should fail with Exception");
}
@Test(expected = IllegalArgumentException.class)
public void getValue_EmptyLine() {
new PairParser("");
fail("This test should fail with Exception");
}
@Test()
public void getValue_BadData() {
PairParser parser = new PairParser("bad data bad data");
assertEquals(0, parser.size());
}
}
答案 1 :(得分:0)
您可以将java.util.regex.Pattern
和java.util.regex.Matcher
用于类似的模式:
^born\stime\s([a-zA-Z0-9\s]*)\s--\skingNumber\s(\d+)\s--\saddress:\s([a-zA-Z0-9\s/]*)\s--\sbirthmonth:\s([a-zA-Z0-9\s]*)$
少写,多做。