简单地:
- 通过仅保留最后 2 行来读取您的文件,
- 然后使用正则表达式提取整数。
对应代码:
try (
InputStream fs = new FileInputStream("data.txt");
InputStreamReader isr = new InputStreamReader(fs, StandardCharsets.UTF_8);
BufferedReader br = new BufferedReader(isr)) {
// Previous line
String prev = null;
// Last line
String last = null;
String line;
while ((line = br.readLine()) != null) {
prev = last;
last = line;
}
// Pattern used to extract the integers
Pattern pattern = Pattern.compile("\\d+");
// Matcher for the previous line
Matcher matcher1 = pattern.matcher(prev);
// Matcher for the last line
Matcher matcher2 = pattern.matcher(last);
// Iterate as long as we have a match in both lines
while (matcher1.find() && matcher2.find()) {
// Value of previous line
int val1 = Integer.valueOf(matcher1.group());
// Value of last line
int val2 = Integer.valueOf(matcher2.group());
// Do something here
}
}
注意:这假设我们在两行中都有完全相同数量的整数,否则您可以比较不相关的值。
如果您使用Java 8的另一种方法,您可以使用非整数作为分隔符,然后依靠splitAsStream(CharSequence input)
将所有整数提取为List
:
...
// Non integers as a separators
Pattern pattern = Pattern.compile("\\D+");
// List of extracted integers in previous line
List<Integer> previous = pattern.splitAsStream(prev)
.filter(s -> !s.isEmpty())
.map(Integer::valueOf)
.collect(Collectors.toList());
// List of extracted integers in last line
List<Integer> current = pattern.splitAsStream(last)
.filter(s -> !s.isEmpty())
.map(Integer::valueOf)
.collect(Collectors.toList());
// Do something here