[英]How to split and parse a text file in Java
對於學校項目,我需要從文本文件中提取消息。 我創建了一個消息類:
public class Message {
private String from;
private String to;
private String body;
public Message(String from, String to, String body) {
this.from = from;
this.to = to;
this.body = body;
}
}
文本文件如下所示:
From: sender
To: Address
blah blah blah
blah blah(can be more then one line)
#(represent end of message)
From: sender2
To: Address2
blah blah blah
blah blah(can be more then one line)
#
我需要從該文本文件創建消息的ArrayList,但是我不確定如何拆分它。 只是為了澄清起見,發件人,收件人和正文用換行分隔,消息以“#”結尾。
我寫了parse()
,它是Message類的解析方法。 我還在main()
編寫了一個簡單的測試,以演示如何將文本文件拆分為單獨的消息。 請注意,此解決方案有局限性。 它將整個文本文件保留為String。 如果文本文件的大小為一個或多個GB,則必須按照此問題找到流處理解決方案。
import org.apache.commons.lang3.StringUtils;
import java.util.ArrayList;
import java.util.List;
public class Message {
private String from;
private String to;
private String body;
public Message(String from, String to, String body) {
this.from = from;
this.to = to;
this.body = body;
}
public String toString() {
return "From: " + from + "\n" +
"To: " + to + "\n" +
"Body: " + body;
}
// creates a messsage object from a string
public static Message parse(String msg) {
if (msg == null || StringUtils.countMatches(msg, "\n") <= 2) {
throw new IllegalArgumentException("Invalid string! Needing a string with at least 3 lines!");
}
// first, find from and to with two splits by new line
String[] splits = msg.split("\n");
// replace the non-informative 'From: " beginning, should it be there
String from = splits[0].replace("From: ", "");
// replace the non-informative 'To: " beginning, should it be there
String to = splits[1].replace("To: ", "");
// the rest is body
String body = msg.substring(msg.indexOf(to) + to.length() + 1, msg.length());
// remove leading and trailing whitespaces
body = StringUtils.trim(body);
return new Message(from, to, body);
}
public static void main(String[] args) {
List<Message> allMessages = new ArrayList<>();
String text = "From: sender\n" +
"To: Address\n" +
"blah blah blah\n" +
"blah blah(can be more then one line)\n" +
"#\n" +
"From: sender2\n" +
"To: Address2\n" +
"blah blah blah\n" +
"blah blah(can be more then one line)";
// split the text by what separates messages from each other
String[] split = text.split("#\n");
for (String msg : split) {
allMessages.add(Message.parse(msg));
}
// print each message to System.out as a simple means of demonstrating the code
allMessages.forEach(System.out::println);
}
}
您可以修改您的Message
類:
class Message {
private String from = "";
private String to = "";
private String body = "";
public void setFrom(String from) {
this.from = from;
}
public void setTo(String to) {
this.to = to;
}
public void addBody(String body) {
if (!this.body.isEmpty())
this.body += '\n';
this.body += body;
}
}
然后只需閱讀構成文本文件的所有行,並逐行創建Message
實例:
private static List<Message> getMessages(List<String> lines) {
final String separator = "#";
final String from = "From:";
final String to = "To:";
Message message = null;
List<Message> messages = new ArrayList<>();
for (String line : lines) {
if (line.startsWith(separator))
message = null;
else {
if (message == null)
messages.add(message = new Message());
if (line.startsWith(from))
message.setFrom(line.substring(from.length()).trim());
else if (line.startsWith(to))
message.setTo(line.substring(to.length()).trim());
else
message.addBody(line);
}
}
return messages;
}
PS要讀取文本文件作為ines列表,請使用例如List<String> lines = Files.readAllLines(Paths.get("data.txt"));
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