[Java知识库]一些本地测试的demo（仅用于日常记录）

1、替换文件后缀名

    @Test
    public void test5() {
        String url = "http://www.baidu.com/aaa.pdf";
        String fileTyle=url.substring(url.lastIndexOf("."));
        System.out.println("文件后缀名为：" + fileTyle);
        String newPath = url.substring(0, url.lastIndexOf(".")) + ".jpeg";
        System.out.println("新路径：" + newPath);

    }

打印结果：

2、使用s%占位符拼接字符串

    @Test
    public void test8() {
        String url = "https://www.baidu.com?str1=%s&str2=002&str3=%s&str5=%s";
        String str1 = "001";
        String str3 = "003";
        Integer str5 = 555;
        String pushUrl = String.format(url, str1, str3, str5);
        System.out.println("转换后推送的链接为：" + pushUrl);
    }

打印结果

3、对日期的一些操作

    @Test
    public void test10() {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//格式化一下时间
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(new Date());
        String today = sdf.format(calendar.getTime());
        String startTime = today.substring(0, 10) + " 00:00:00";
        calendar.add(Calendar.DAY_OF_MONTH, -1);
        String beforeOneDay = sdf.format(calendar.getTime());
        calendar.add(Calendar.HOUR_OF_DAY, -1);
        String beforeTwentyFiveHours = sdf.format(calendar.getTime());
        System.out.println("当天的零点时间：" + startTime);
        System.out.println("当前时间：" + today);
        System.out.println("一天前的时间：" + beforeOneDay);
        System.out.println("25小时前的时间：" + beforeTwentyFiveHours);
    }

运行结果：

4、mybatisplus使用模糊查询

EntityWrapper<Question> entityWrapper = new EntityWrapper();
        //根据问卷名称模糊搜索
        entityWrapper.like(StringUtil.isNotEmpty(questionName),"name", questionName);
        entityWrapper.orderBy("created_at",false);
        return selectPage(page, entityWrapper);