java中的优雅写法

ゝ一纸荒年。 2024-03-27 16:37 14阅读 0赞

//字符串拼接
    String.format("%s%s","Axx","Bxx");
    
    //List拼接成String
    StringUtils.join(list,"、");
    
    // 按zdlxkzsxId分组
    Map<Long, List<String>> zdxxExPropMap = zdxxkzsxes.stream().collect(Collectors.groupingBy(Zdxxkzsx::getZdlxkzsxId,
                    Collectors.mapping(Zdxxkzsx::getExProp, Collectors.toList())));
    
    //判断List中元素是否都相等
    list.stream().distinct().count() <= 1;
    list.isEmpty() || list.stream().allMatch(list.get(0)::equals);
    
    //判断List中是否存在某个元素
    list.stream().anyMatch(obj -> "str2".equals(obj));
    
    //获取LocalDateTime的开始时间和结束时间
    queryReqDto.getTjrqF().with(LocalTime.MIN)
    queryReqDto.getTjrqT().with(LocalTime.MAX)
    
    DecimalFormat df = new DecimalFormat();
    BigDecimal data = new BigDecimal(0.305607809);
    String pattern = "0.00%";//120340.56%
    df.applyPattern(pattern);
    System.out.println("采用" + pattern + "模式格式化后："+df.format(data));//40.56%
    
    BigDecimal data1 = new BigDecimal(60.305607809);
    String pattern1 = "-00.000kg";
    df.applyPattern(pattern1);
    System.out.println("采用" + pattern1 + "模式格式化后："+df.format(data1));//-60.306kg
    
    // String转java对象
    ResultDto resultDto = JSONObject.parseObject(JSONObject.toJSONString(obj), new TypeReference<>() {});
    ResultDto resultDto = JSONObject.parseObject(JSONObject.toJSONString(obj), ResultDto.class);
    
    //两个List去重
    list1.removeIf(obj1 -> list2.stream().anyMatch(obj2 -> obj2.getCode().equals(obj1.getCode())));
    
    //取每个月的第一天和最后一天
    calendar.set(Calendar.DAY_OF_MONTH,lastMonthFirstDay.getActualMinimum(Calendar.DAY_OF_MONTH));
    calendar.set(Calendar.DAY_OF_MONTH,lastMonthFirstDay.getActualMaximum(Calendar.DAY_OF_MONTH));

SQL INNER JOIN limit慢的优化写法：

FROM  
wljs\_yt\_shjsxx jsxx  
INNER JOIN (  
SELECT  
shjsxx\_id  
FROM  
wljs\_yt\_shjsxx  
LIMIT 20  
) jsxx1 ON jsxx.shjsxx\_id = jsxx1.shjsxx\_id