符合或更晚。不需要字符串，也不需要java.sql.*类

从哪里获得java.time类

• 然后
  • 内置的
  • 标准JavaAPI的一部分，带有捆绑实现
  • Java9添加了一些次要功能和修复
• 及
  • 大部分java.time功能都在中向后移植到Java6和Java7
• • 更高版本的Android捆绑包实现了java.time类

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  • 对于早期的Android（不相关（我不知道你在问什么），但答案要么是>0，因为根据数据库中的日期2018-06-12应该等于当前日期。但在这种情况下，它不是。我只是以<0Yes.

    rs.getDate（）

    返回一个日期，没有时间组件（或者更准确地说，时间成分是午夜）。但是

    newdate（）

    提供当前日期和时间。请使用dateFormat.format（rs.getDate（5））在所有if语句中，所有语句都将采用相同的格式。您需要的是

    LocalDate

    from。它是一个没有时间的日期，因此不能对您耍这种把戏。另外，

    java.time

    使用起来更好。或者使用java 8中引入的日期/时间API，

    sqlDate.toLocalDate（）.compareTo（LocalDate.now（））

    ：PThanks，我从来没有想过时间也包括在内。这是如此简单。并在顶部为您升级到现代API。热烈推荐。感谢您的详细回复！但现在我面临一个新问题，我不知道为什么，但当您尝试在DB中存储日期时，没有发生任何错误或任何错误事情和日期不会更新，知道吗？@Kristofer我添加了一个完整的H2数据库示例。至于：（a）你在

    updateDate

    SQL中声明了两个占位符，但你只设置了其中一个。（b）你从来没有时间执行准备好的语句。因此没有尝试更新。（c）MySQL语法中是否允许回勾字符？据我所知，标准SQL中不允许回勾字符。（d）提示：使用try with resources语句，这是Java 9中新改进的语句。

    private static void Resetter() throws ParseException, SQLException {
        String host = "****";
        String username = "root";
        String mysqlpassword = "";
    
        //Querys
        String query = "select * from accounts";
        String queryy = "update accounts set daily_search_count = 0 where id = ?";
        Connection con = DriverManager.getConnection(host, username, mysqlpassword);
        Statement st = con.createStatement();
        ResultSet rs = st.executeQuery(query);
    
        DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd");
        dateFormat.setTimeZone( TimeZone.getTimeZone( "UTC" ));
        Date currentDate = new Date();
    
        while(rs.next()){
            System.out.println(dateFormat.format(currentDate));
            if (rs.getDate(5).compareTo(currentDate) > 0) {
               // System.out.println("Database-date is after currentDate");
            } else if (rs.getDate(5).compareTo(currentDate) < 0) {
               // System.out.println("Database-date is before currentDate");
                PreparedStatement updatexdd = con.prepareStatement(queryy);
                updatexdd.setInt(1, rs.getInt(1));
                int updatexdd_done = updatexdd.executeUpdate();
            } else if (rs.getDate(5).compareTo(currentDate) == 0) {
               // System.out.println("Database-date is equal to currentDate");
            } else {
                System.out.println("Any other");
            }
        }
    }
    

    Calendar cal = Calendar.getInstance();
    cal.set(Calendar.HOUR_OF_DAY, 0);
    cal.set(Calendar.MINUTE, 0);
    cal.set(Calendar.SECOND, 0);
    cal.set(Calendar.MILLISECOND, 0);
    Date currentDate = cal.getTime();
    

    Date currentDate = new java.sql.Date(System.currentTimeMillis());
    

    while(rs.next()){
        System.out.println(dateFormat.format(currentDate));
        if (rs.getDate(5).after(currentDate)) {
           // System.out.println("Database-date is after currentDate");
        } else if (rs.getDate(5).before(currentDate)) {
           // System.out.println("Database-date is before currentDate");
            PreparedStatement updatexdd = con.prepareStatement(queryy);
            updatexdd.setInt(1, rs.getInt(1));
            int updatexdd_done = updatexdd.executeUpdate();
        } else {
           // System.out.println("Database-date is equal to currentDate");
        }
    }
    

    LocalDate today = LocalDate.now( ZoneOffset.UTC ) ;
    Instant instant = myResultSet.getObject( … , Instant.class ) ;  // Retrieve a `TIMESTAMP WITH TIME ZONE` value in database as an `Instant` for a date with time-of-day in UTC with a resolution as fine as nanoseconds.
    LocalDate ld = instant.atOffset( ZoneOffset.UTC ).toLocalDate() ;  // Extract a date-only value without time-of-day and without time zone.
    
    if ( ld.isBefore( today ) ) { … }       // Compare `LocalDate` objects.
    else if ( ld.isEqual( today ) ) { … }
    else if ( ld.isAfter( today ) ) { … }
    else { … handle error }
    

    LocalDate ld = myResultSet.get( … , LocalDate.class ) ;  // Retrieving from database.
    myPreparedStatement.setObject( … , ld ) ;  // Storing in database.
    

    Instant instant = myResultSet.get( … , Instant.class ) ;  // Retrieving from database.
    myPreparedStatement.setObject( … , instant ) ;  // Storing in database.
    

    Boolean overdue = someLocalDate.isAfter( otherLocalDate ) ;
    

    OffsetDateTime odt = instant.atOffset( ZoneOffset.UTC ) ;  
    LocalDate ld = odt.toLocalDate() ;   // Extract a date-only value without time-of-day and without time zone.
    

    LocalDate today = LocalDate.now( ZoneOffset.UTC ) ;  // Specify the offset/zone by which you want to perceive the current date.
    

    if ( ld.isBefore( today ) ) { … }
    else if ( ld.isEqual( today ) ) { … }
    else if ( ld.isAfter( today ) ) { … }
    else { … handle error }
    

    String output = LocalDate.now().toString() ;  // Ex: 2018-01-23
    

    try (
        Connection conn = DriverManager.getConnection( "jdbc:h2:mem:trashme" )
    ) {
        String sql = "CREATE TABLE " + "tbl_" + " (\n" +
                         "  uuid_ UUID DEFAULT random_uuid() , \n" +  // Every table should have a primary key.
                         "  when_ DATE \n" +                          // Three columns per the Question.
                         " );";
        try (
            Statement stmt = conn.createStatement() ;
        ) {
            stmt.execute( sql );
        }
    
        sql = "INSERT INTO tbl_ ( when_ ) VALUES ( ? ) ;";
        LocalDate start = LocalDate.of( 2018 , Month.JANUARY , 23 );
        LocalDate ld = start;  // Keep the `start` object for use later.
        try (
            PreparedStatement ps = conn.prepareStatement( sql )
        ) {
            for ( int i = 1 ; i <= 10 ; i++ ) {
                ps.setObject( 1 , ld );
                ps.executeUpdate();
                // Prepare for next loop.
                int randomNumber = ThreadLocalRandom.current().nextInt( 1 , 5 + 1 ); // Pass minimum & ( maximum + 1 ).
                ld = ld.plusDays( randomNumber ); // Add a few days, an arbitrary number.
            }
        }
    
        // Dump all rows, to verify our populating of table.
        System.out.println( "Dumping all rows: uuid_ & when_ columns." );
        sql = "SELECT uuid_ , when_ FROM tbl_ ; ";
        int rowCount = 0;
        try (
            Statement stmt = conn.createStatement() ;
            ResultSet rs = stmt.executeQuery( sql ) ;
        ) {
            while ( rs.next() ) {
                rowCount++;
                UUID uuid = rs.getObject( 1 , UUID.class );
                LocalDate localDate = rs.getObject( 2 , LocalDate.class );
                System.out.println( uuid + " " + localDate );
            }
        }
        System.out.println( "Done dumping " + rowCount + " rows." );
    
    
        // Dump all rows, to verify our populating of table.
        System.out.println( "Dumping rows where `when_` is after " + start + ": uuid_ & when_ columns." );
        sql = "SELECT uuid_ , when_ FROM tbl_ WHERE when_ > ? ; ";
        rowCount = 0; // Reset count.
        final PreparedStatement ps = conn.prepareStatement( sql );
        ps.setObject( 1 , start );
        try (
            ps ;
            ResultSet rs = ps.executeQuery() ;
        ) {
            while ( rs.next() ) {
                rowCount++;
                UUID uuid = rs.getObject( 1 , UUID.class );
                LocalDate localDate = rs.getObject( 2 , LocalDate.class );
                System.out.println( uuid + " " + localDate );
            }
        }
        System.out.println( "Done dumping " + rowCount + " rows." );
    
    } catch ( SQLException eArg ) {
        eArg.printStackTrace();
    }