我怎样才能只检索日期？JAVA

我从日志文件中读到的，但有点像

2021-04-29 18:16:30.038[POOL-5-THREAD-1]批量发布策略端到端|开始：2021-04-29 18:16:30 |结束：2021-04-29 18:16:30 |恢复：10MS

我要2021-04-29

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;
public class Main{

     public static void main (String[] args)throws Exception{
     demoReadall();
     }

     public static void demoReadall(){
          
          try{
               FileInputStream fstream = new FileInputStream("testlog.log");
               BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
               String strLine;
               /* read log line by line */
               while ((strLine = br.readLine()) != null)   {
                 /* parse strLine to obtain what you want */
                 System.out.println (strLine);
               }
               fstream.close();
            } catch (Exception e) {
                 System.err.println("Error: " + e.getMessage());
            }
     }
}

谢谢。

你是说这个吗

问候

输出：

2021-04-29
2021-04-29
2021-04-29

代码：

在您的代码中，它将如下所示：

import java.util.*;
import java.lang.*;
import java.util.regex.*;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;

public class Main{

     public static void main (String[] args)throws Exception{
     demoReadall();
     }

     public static void demoReadall(){
          
          try{
               FileInputStream fstream = new FileInputStream("testlog.log");
               BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
               String strLine;
               Pattern pattern = Pattern.compile("(\\d{4}-\\d{2}-\\d{2})");
               Matcher matcher;
               /* read log line by line */
               while ((strLine = br.readLine()) != null)   {
                matcher = pattern.matcher(strLine);

                while (matcher.find()) {
                    String match = matcher.group();
                    System.out.println(match);
                }
                   
                 /* parse strLine to obtain what you want */
                 //System.out.println (strLine);
               }
               fstream.close();
            } catch (Exception e) {
                 System.err.println("Error: " + e.getMessage());
            }
     }
}

---

String date=strLine.split（“”[0]应该可以。
strLine.substring（0,10）
也可以。线程“main”java.lang中出现错误异常。错误：未解决的编译问题：在main.main（main.java:10）我输入错误，只需将“public class MyClass{”替换为“public class main{”您解决了吗？请在此处查看您的工作代码：好的。非常感谢。然后将其标记为答案。谢谢。
import java.util.*;
import java.lang.*;
import java.util.regex.*;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;

public class Main{

     public static void main (String[] args)throws Exception{
     demoReadall();
     }

     public static void demoReadall(){
          
          try{
               FileInputStream fstream = new FileInputStream("testlog.log");
               BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
               String strLine;
               Pattern pattern = Pattern.compile("(\\d{4}-\\d{2}-\\d{2})");
               Matcher matcher;
               /* read log line by line */
               while ((strLine = br.readLine()) != null)   {
                matcher = pattern.matcher(strLine);

                while (matcher.find()) {
                    String match = matcher.group();
                    System.out.println(match);
                }
                   
                 /* parse strLine to obtain what you want */
                 //System.out.println (strLine);
               }
               fstream.close();
            } catch (Exception e) {
                 System.err.println("Error: " + e.getMessage());
            }
     }
}